The amount of thorough supervision to which a vessel is subjected

while under construction, renders the fear of unseaworthiness, from

either defective construction or equipment, the least reasonable

of all the fears with which ocean navigation is regarded. It is in

later circumstances, and concerning matters of a more extraneous

character, that the most justifiable fears may be entertained

regarding a vessel’s safety. Overloading, improper stowage, bad

management, under-manning, insufficient repair, besides the numerous

inevitable and unforeseen circumstances incidental to sea-voyaging,

may be instanced as the causes to which the greatest losses are

attributable.[4] Few instances of loss from structural defects are

adduceable, and even in these, causes of a more or less extraneous

character are associated with the loss. On the other hand, instances

could be multiplied where vessels sustaining the casualties which

rough weather or rank carelessness make always imminent have come

out of the ordeal with credit to the constructors. One notable case

may be instanced. The _Arizona_, of the Guion Line, some time after

being put on the Atlantic service, while steaming at a speed of 14

knots, and almost in mid-Atlantic, ran into an iceberg of gigantic

dimensions, and notwithstanding that the force of the concussion

smashed her bows for a length of 20 feet into an unrecognisable mass,

she kept afloat, and reached a port of safety.

Where, as has already been indicated, there is such close oversight

and thorough supervision—where, indeed, the real interests of every

party honestly concerned lie so clearly in the high qualities of

construction—nothing short of such results as the foregoing should be

expected. The insurance companies, on whom the burden (monetary at

least) of loss at sea ultimately falls, see it their interest to know

that those registration societies, on whom they rely for guarantee

as to a vessel’s structural and general efficiency, are themselves

efficient and trustworthy authorities. These societies, known as

Lloyd’s, Liverpool Underwriters, and Bureau Veritas, Registries, in

spite of the dread as to business rivalry affecting injuriously their

standards of classification, have still a high criterion, and enjoy

the confidence of insurance societies and shipowners alike.

Shipowners themselves, notwithstanding some examples to the contrary,

are, and have always been, anxious and painstaking seekers after

thoroughness; not merely mercenary grubs, sacrificing considerations

of safety to features promising exemption from tonnage or other

registration dues, and perhaps the extinction of a rival. Some of the

best British vessels, notably those of the Cunard Line, are unclassed

at the registries, but have been built under private survey. The

well known boast of the Cunard Company that not a single life has

been lost by mishap at sea during their long and extensive service,

is eloquent testimony to the care exercised in the construction and

management of ships. It is the practice of some companies to effect

classification in two, sometimes three, separate registries, and

the number of inspectors employed to superintend the work of

construction, over and above the surveyors of the registries and

the overseers of the firms, is in some instances astonishing. The

crowning case of all is that of the building firms themselves—many

shipbuilders unquestionably being conscientious and thorough to a

degree which simply mocks this great array of supervision.

In the outfit of vessels correspondingly close attention is paid to

those features, fixed or portable, which contribute to the safety

of the ship and the welfare of passengers. The universal adoption

of steam winches for working cargo enables the pumps communicating

with the holds to be wrought by steam, through levers attached to

the barrel ends of the winches. Special donkey-engine pumps, in

addition, are now employed in all the higher class vessels, and

automatic means of registering the quantity of water in the holds are

beginning to be introduced. Provision against outbreaks of fire, no

less than against foundering, has been receiving greater attention

than formerly. Many of the first-class mail steamships are fitted

with fire-pipes leading to every compartment, and which convey at the

turning of a valve a charge of steam sufficient to extinguish the

most serious outbreak. Lowering and detaching gear for life-boats is

now a necessary part of every first-class steamer’s equipment. Over a

dozen different apparatuses for effecting this very important purpose

are at present in the market, some of which are admirably adapted for

safe and speedy working, even in the hurry and panic which too often

accompanies cases of shipwreck.

Important as these devices are for saving life and property in event

of casualty, the appliances which contribute to the prevention of

casualty at all, are perhaps more so. This is a gradually increasing

and improving element in ships’ outfit. Conspicuous among this class

of articles are navigational instruments, and of these perhaps the

most noteworthy are the instruments with which the name of Sir

William Thomson is associated, although many others, in use or

awaiting adoption, and designed for equally important purposes, might

be referred to, did space permit.

Within the period covered by this review, this eminent inventor has

introduced an instrument which enables soundings to be taken while

vessels are going at full speed, at depths of 100 fathoms and under.

The sounding line adopted is a fine steel wire, such as is used by

pianoforte makers, which passes through the water with very little

resistance, and can be sent to the bottom by a light weight or

sinker, even when the ship is going full speed. Fastened to a short

length of rope, near the sinker, there is a brass tube, in which is

placed a glass tube two feet long, closed at one end and open at the

other. This glass tube is coated inside with chromate of silver. As

the sinker goes down, the air in the tube becomes compressed, and

sea water rises up inside, the height to which it rises depending on

the depth, from the surface, to which the glass tube goes down. As

the sea water rises in the tube, the salt of the water acts on the

chromate of silver and changes the colour from red to white; thus a

mark is left on the glass tube showing the height to which the sea

water rises, from which the actual depth may be at once measured

by a prepared scale. By means of this sounding machine a ship can

feel her way round a coast in a fog without reducing speed. In later

instruments the inventor has devised another form of automatic gauge,

which obviates the use of glass tubes, and is a decided improvement

on the gauge here described.

The well-known Improved Mariner’s Compass introduced by Sir W.

Thomson enables the magnetism of the ship to be completely corrected

instead of only approximately. This is attained by the use of several

small needles instead of one or two large ones. The requisite

steadiness of the compass card is obtained by means of an aluminium

rim suspended round the edge of the card. The extreme lightness of

the card reduces greatly the wear of the needle point supporting the

compass. Along with the compass the inventor supplies an azimuth

mirror which greatly facilitates observations either on a point of

land or on a star, the whole invention proving from experience an

almost indispensable item of outfit for well-appointed vessels.

The care and ingenuity expended on the question of ship safety must

not, however, be measured simply by the amount of attention and skill

exercised in constructing and outfitting vessels of the common type.

The question has very naturally occasioned many distinct novelties

in ship design. Some of these have been directly designed to secure

safety, but the greater number have aimed at combining with safety

the other qualities of speed and comfort; as in the instances given

in the previous chapter. The success attained in practice, it need

scarcely be said, has hitherto been but partial.

The problem of rendering ships absolutely unsinkable has, from very

early times, received attention from many concerned in shipbuilding

and navigation. Propositions and trials have been made from time to

time, without as yet any very marked success attending any of them.

Various plans have been submitted for safety-ships, the general

principle of which consists in forming the ship into two or more

distinct and entire portions, and in the event of one sustaining

damage by collision or otherwise, those remaining to be disconnected

and sent adrift—presumably with all passengers on board.

Other life-saving devices, while interfering somewhat with the

original structure, have simply been intended to use or modify

existing features or material on board ship. Two of these which have

received attention from the Scientific Societies may be shortly

described as examples of the class of devices referred to. One was

the proposition of Mr Jolly, M.A., of the Royal Navy, laid before

the Institution of Naval Architects in 1874; the other being that

of Mr Gadd, submitted to the Manchester Mechanical Society in 1879.

Mr Jolly’s proposal was to construct what he felicitously termed

the “ark saloon,” an erection on the upper deck, and resembling

very closely an ordinary deck-house, but instead of being built

permanently on the vessel, it was to be an independent structure

capable of being readily disconnected, and “while answering all the

purposes of accommodation found in ordinary deck-houses, to have

within it hidden resources capable of converting it when afloat

into a perfectly navigable vessel.” Mr Gadd’s proposal was to form

the upper portion of the bulwarks of ships of loose sections 12-ft.

long, composed chiefly of hollow, thin metallic tubes. These sections

when immersed in the water would form so many pontoons, and would be

provided with cords and loops along their sides, and in the event

of the ship going down would be lifted out of their place by the

action of the water. Objections on economical grounds to Mr Jolly’s

scheme, fully pointed out by members of the Institute, apply almost

equally to the proposal of Mr Gadd. The expense involved in their

application would far outbalance in the eyes of the shipowner the

possible service they could render. No provision was made by Mr Jolly

for launching his ark saloon, thereby limiting its use to cases of

foundering; and even in event of this, the “ark” was only to be so

in name until the good ship should “go under,” and leave the saloon

serenely floating—presumably with all souls inside. The difficulty in

Mr Gadd’s proposal, of at once making the bulwarks easily floatable

and structurally efficient for the resistance of heavy seas,

seriously detracted from its feasibility.

It would be a somewhat heavy task to make adequate note of all

the varied proposals and patented inventions for the preservation

of life at sea. Some of these, as in the foregoing instances, are

proposals affecting structural features; but others, and by far the

most numerous, are simply adjuncts to the vessel. Ingenuity has

been specially directed of late towards bringing into efficient

requisition, in event of impending shipwreck, the commonest items of

a ship’s outfit. This has been abundantly evidenced in the several

naval exhibitions held within the past three years in various parts

of the country. Firms whose work lies in cork and Indiarubber

manufactures have there exhibited in great profusion various forms

of life-belts, life-buoys, life-saving mattresses and pillows, and

life-saving dresses. Others, availing themselves of larger items,

have shown life-saving adaptations of deck-seats, deck-houses, and

bulwarks made into the form of life-rafts. Not a few of these devices

have received adoption in our passenger-carrying steamships, and

their more general use—especially if accompanied by proper knowledge

of how they may best be taken advantage of—would materially help to

rob shipwreck of some of its terrors at least, if not of its dire

fatalities. It has been urged in this connection—and the plea is

eminently reasonable—that Parliament should invest the Board of Trade

with proper powers—if that Body is not already vested with all that

is requisite—to take the matter of life-saving appliances thoroughly

and practically in hand, and by means of experiments in all kinds of

weather to determine which are the best means of saving life under

different conditions. Having done this, also to draw up rules for

the proper stowage and use of such appliances on board ship, and to

see that such rules are strictly observed, and that no vessel be

permitted to go to sea which is not so equipped.

* * * * *

The development in the size of steamships not only affects the

quality of safety, but also in various ways the element of comfort at

sea. The greater length, for instance, is calculated to neutralise

the longitudinal oscillation, the effects of which are so often fatal

to the comfort of passengers. Again, the great length affords an

advantage in the way of allowing better state-room accommodation; all

the rooms, or a larger proportion of them, being next the vessel’s

side, and consequently more airy and better lighted. It is not,

however, in the increased length so much as in the development of all

three dimensions, and especially in the increased ratio of breadth

to length, that modern types of steamships are enhanced in the

qualities of safety and comfort. Mistaken or imperfect notions as to

the ratio most desirable for speed, have kept in perpetuity types of

steamers which the fuller light of modern scientific investigation

has shown to be undesirable. Great beam is now believed to be not

incompatible with great speed, and even apart from questions of speed

the advantages accruing from breadth are better appreciated.

As an illustration of this movement, one of the more recent of

the many transatlantic mail steamships may be instanced. In the

_Aurania_, of the Cunard Company, the proportions—although perhaps

only in the line along which modern professional ideas tend—are

certainly in advance of the general practice with regard to vessels

of her great size. The dimensions of the _Servia_, the _Alaska_,

and the _City of Rome_—three vessels comparable with the _Aurania_

as constituting the largest merchant vessels afloat—all give a

proportion of 10 beams to the length. The _Aurania’s_ dimensions—470

feet by 57 feet by 39 feet—show her to have only about 8¼ beams to

length. The success of the older type of vessel having proportions

somewhat similar to this “modern instance” has in no material

sense been eclipsed by the narrow types which subsequently for

so long prevailed. Availing themselves of that freedom which

independence of the registration societies yield—their vessels not

being “classed”—the Cunard Coy determined to adopt the old-time

proportions. The step has been justified, in so far as affected by

the matter of speed, the powerful vessel, at her trials on the Clyde,

having attained a mean speed of 17¾ knots, or 20½ statute miles, per

hour. The stable qualities due to the great breadth of the _Aurania_

has in actual service further confirmed the wisdom of the change. The

magnificent vessels presently building on the Clyde for the Cunard

Coy., though between 20 and 30 feet longer, are the same breadth as

the _Aurania_, _i.e._, 57 feet. This is accounted for by the fact

that the breadth of beam fixed for the _Aurania_ was the largest

amount permissible, having regard to the breadth of entrance of the

largest dock in New York. This _en passant_ is worthy of notice as

giving colourable justification to the complaints sometimes made that

civil engineers are urged to progress in dock accommodation only by

shipbuilders treading on their heels.

Coincident with the changes made in the dimensions and structure

of vessels, there are numerous features of enhanced comfort for

passengers and crew which are deserving of notice. Notably is

this manifest in the arrangement of saloons and state-rooms—their

appointment, lighting, and ventilation. The character of steamships

for the great ocean highways in this respect is above and beyond

anything which Board of Trade enactments seek to secure. The amount

of spirited competition itself on those services, acts as an

efficient promoter of excellence in design and equipment.

It is now the prevailing fashion to appropriate that part of a

steamer just before the engine and boiler hatchways for the principal

saloon and first-class berthing, and it has so many advantages over

the old plan of locating these apartments in the poop or after

extremity of the vessel that its adoption in large steamers of the

passenger-carrying trade has become all but general. Some of these

advantages may be briefly enumerated. They are:—ampler and airier

saloon space: the plumbness of the vessel’s sides permitting a

saloon completely athwartship, which is scarcely practicable in

the conventional situation aft, because of the curvature of sides;

increased facilities for ventilation; purer air; freedom from the

noise and vibration caused by propeller; comparative immunity from

the effects of “pitching” or longitudinal oscillation.

Nothing, perhaps, in connection with improved saloon accommodation

strikes one so much as the increased height between decks now

prevalent. While from six-and-a-half to seven-and-a-half feet

was considered sufficient some years ago, it is now the practice

in first-class steamers to make the height as much as from

eight-and-a-half to nine-and-a-half feet. The feeling of spaciousness

this change contributes to the saloons, as well as the scope it

yields for architectural treatment of the walls, are not the least

gratifying results of the improvement. How much the latter result

has been taken advantage of in our modern passenger steamships need

scarcely be told, as their architectural and decorative character is

often and eloquently enlarged upon by delighted voyagers.

[Illustration: FIG. 9.

LONGITUDINAL SECTION OF GRAND SALOON IN _S.S. America_, SHOWING

DOME-ROOF.]

A noteworthy feature in improved saloon accommodation is the

provision of music rooms or social halls, which are usually situated

above the dining saloons, and connected or made one therewith by

means of light and ventilation wells placed in the centre. The

size and ornamentation of these, and the light and air they are

the means of admitting, contribute in a very marked degree to the

spaciousness, beauty, and comfort of the main saloon. By recent

special modifications in the deck structure, several builders on the

Clyde—notably Messrs J. & G. Thomson—are rendering this feature of

greater value than ever. In the National Line Steamship _America_,

just finished by the firm named and to which attention has already

been directed, the Grand Saloon is a splendid apartment, extending

from side to side of the vessel, and measures over eighty feet in

length. Its size and height are augmented in a remarkable degree by

the fitting of a dome-roof extending in height through two tiers

of decks, and embracing about half the length of saloon. This

feature—some conception of which may be gathered from the sketches

shown by Figs. 9 and 10, is altogether free of athwartship beams,

and practically gives to the saloon a clear height of 18 feet. The

crown of the dome is formed of beautifully-executed stained glass,

finished round its base in a richly coloured frieze formed of panels

containing well-executed oil paintings. The whole feature, for

structure, ampleness, and ornamentation, is a noteworthy advance in

the way of rendering the saloons of steamships more comfortable—not

to say palatial—and reflects the utmost credit on the building firm.

[Illustration: FIG. 10.

CROSS SECTION OF GRAND SALOON IN _S.S. America_, SHOWING DOME-ROOF.]

In several vessels built within recent years on the Clyde there has

been adopted—in addition to the athwartship middle length saloon, a

curious and complete reversal of the traditional arrangement with

respect to accommodation for the crew. The plan, one would think,

must shock the orthodox sentiment of our seamen, whatever they may

think of its utility. A few strokes of the draughtsman’s pencil, and

_per saltum_ “Jack” and his “castle” are transported to the poop, and

the precincts so long sacred to his use are prostituted to the lounge

and the tobacco pipe of the pampered “land-lubber”—_i.e._, they form

a luxuriant smoking saloon for passengers.

Of the multifarious ways in which modern invention and skill are laid

under contribution to the end that voyagers shall have the maximum

of safety and comfort on board ship, the system of electric lighting

now so extensively adopted is not the least noteworthy. It is only

about three years ago since the application of the incandescent form

of electric lamp on board ship was first tried. The success of the

system and its rapid extension during the subsequent period has been

remarkable, and is a matter upon which electricians, shipowners, and

sea voyagers are alike to be congratulated. In every well-appointed

passenger ship for ocean service, the electric light has already

supplanted the former method of lighting the saloons, state-rooms,

and machinery spaces, by means of oil lamps, which has so often

proved a fruitful source of annoyance to passengers and crew, if not,

indeed, of positive danger to the vessel herself.

The advantages of the change are such as constitute the electric

light an invaluable acquisition on board every modern passenger

steamship. The light gives off very little heat, there is no smell,

no products of combustion to produce headaches and sickness. No

matches are required, and the danger from fire is absolutely reduced

to a minimum. The light requires little or no attention on the part

of stewards, for it is only requisite that a man be sent round once

a day to see whether any of the lamps require renewal, and the

renewal of a lamp is performed as simply as trimming the wick of an

oil lamp or placing a fresh candle into a candlestick. The danger,

annoyance and time, formerly spent in storing up and dealing out

large quantities of paraffin or other oils, are completely obviated.

The lamps are as easily subject to the control of the passenger as

ordinary gas jets. Instead of the flickering and somewhat clumsy oil

lamps, the electric system presents, encased in neat, tiny, glass

globes, a steady, mellow white light, the adaptability of which to

any conceivable position or design is one of its most beautiful

properties. The artistic grouping of the electric incandescent lamps,

and their combination with the architectural features of saloons,

are matters to which the forms adopted for the best known lamps—the

Edison & Swan types—specially lend themselves. A single Edison lamp

is shown by Fig. 11.

The work in electric lighting on board ship for the year 1883 shows

how firmly the electric system has become established as the only

system for first-class passenger vessels. The report of the Edison

& Swan United Companies embraces the work on thirty-one vessels,

including three Indian troopships (and four more on order), four

vessels for the Clan Line, one for the Peninsular and Oriental

Company, one for the Union Steamship Company, three for the Cunard

Company, three for the British India Steam Navigation Company, three

for the New Zealand Shipping Company, and so on. The list of Messrs

Siemens Brothers amounts to twenty high-class vessels, including the

_Arizona_, the _Servia_, the _Aurania_, the _City of Rome_, the _City

of Chicago_, the _Austral_, the _Germanic_, and the _Massilia_. These

two firms thus give fifty-one vessels, and adding those entrusted to

outsiders—four in all—affords a total of fifty-five, representing an

aggregate of not less than 11,000 incandescent lamps.

[Illustration: FIG. 11.

EDISON LAMP.]

The application of the electric light on board ship to the purposes

of signalling, as a substitute for the ordinary system of oil

lanterns, has been fully shown in theory and already partially

effected in practice, but its development in this direction is

necessarily retarded by considerations which do not affect its

use in the interior of vessels. Vessels traversing the ocean in

darkness are necessarily dependent one on the other for the means

of knowing their proximity, and as the electric light much exceeds

in power and brilliancy that of oil lanterns, it would have the

effect of eclipsing the latter even within a large radius. The

adoption of the electric light for this very important purpose

would, therefore, have to be pretty much a simultaneous and general

movement throughout the ships of the various companies, if not of

the various nations. Apart from such considerations, however, other

objections have been instanced to the appropriation of the electric

light for this purpose. Difficulty, it is said, has been experienced

in distinguishing the colours pertaining to the port and starboard

side-lights, and fears are entertained regarding the liability of

the light, or the machinery employed in generating the current, to

suddenly fail in its action. Few of the objections named, of course,

amount to very serious obstacles, and as the system is yet so much

in its infancy, it may well happen that a few years will witness all

that is here foreshadowed.

Short of this universal and complete appropriation of the electric

light for signalling, however, it has been introduced with gratifying

results in mercantile steamers for various important purposes—_e.g._,

for lighting up the decks and surrounding wharfage during the work

of loading or disembarking cargo; for projecting a flood of light

ahead of a vessel’s course where navigation is difficult, and when

danger in the shape of rocks or icebergs is imminent. The employment

of the light in the way last named has been specially extended in the

case of vessels intended for naval warfare. By its powerful aid the

position and tactics of the enemy, the configuration of forts about

to be assailed, or the nature of the land where it is proposed to

disembark, can all be revealed, with a minuteness almost as perfect

as that due to the light of day.

Another feature on board ship affecting most intimately the

well-being and comfort of passengers—too often, indeed, the safety of

the ship itself—is that of ventilation. The thorough and efficient

ventilation of ships is a feature which only during very recent times

has received from shipowners and shipbuilders the amount of attention

it deserves. The inadequacy of the methods of ventilation existing

in emigrant ships, and as applied to holds for the ventilation of

cargoes, engaged public attention very considerably a few years ago.

The explosion on board the _Doterel_, with other like casualties,

resulted in the appointment of a Royal Commission to inquire into the

ventilation of ships. The prominence thus given to the subject and

the experience then gained, have been fruitful of increased regard

for efficiency in ship ventilation. In the absence for such a long

time, however, of any system capable of universal application and

having at once the merits of efficiency and cheapness, shipowners

have adhered to old-fashioned, unscientific, and ineffective methods

long after the invention of improved systems, one or other of which

would have well repaid adoption.

In ways and to an extent which may perhaps have been made evident

in the previous pages, the introduction of the electric light is

of itself greatly advantageous in this connection. One striking

peculiarity of the change perhaps requires more explicit statement.

This is the curious fact—patent enough to all who know anything of

the properties of the incandescent light—that what is the very life

of oil or other lights, is to it, certain death. The element thus

vitally concerned is, of course, oxygen; and it need not be more than

hinted that in existing so entirely without this element—at all times

a great desideratum in passenger ships—the electric light is a vast

benefactor to all who “go down to the sea in ships.”

Many highly-improved methods of ventilation are now open to the

shipowner; the number of patented systems in use or awaiting

adoption being adequate testimony to the widespread attention

bestowed upon the subject. These divide themselves into two general

classes:—firstly, systems which aim at providing an efficient

self-acting series of ventilating pipes in which the natural current

or that induced by the vessel’s own speed through the atmosphere, is

the only force utilised; and secondly, those in which machines driven

by steam power are employed to produce fresh currents or extract

vitiated atmosphere.

[Illustration: FIG. 12.]

[Illustration: FIG. 13.]

Various forms of ventilators, belonging to the first-named class,

have been introduced into many ocean-going passenger vessels within

recent years, the result being a considerable improvement in the

sanitary condition of the more confined portions of vessels. One of

the most approved of these, receiving specially extended adoption,

amounting as it does to a highly perfected system, may be noticed

a little in detail. This is the form of ventilator patented and

introduced by Messrs R. Boyle & Son, the well known ventilating

engineers of London and Glasgow, consisting of upcast and downcast

shafts fixed above deck, communicating with the interior of vessel by

a system of piping led to the various compartments. The upcast, or

“air pump” ventilator, as the patentees term it, consists of a fixed

head having an ingenious arrangement of louvre webs, whereby the wind

impinging upon it from any direction, creates a current and exhausts

the air from the cylinder of which the head is part, the foul air

from below immediately ascending to supply the place of the air

extracted. A continuous and powerful upward current is thus induced,

and the head is so devised as to effectually prevent down-draught

or the inlet of water. The elevation and plan of this ventilator

is shown by Figs. 12 and 13. In Fig. 13, 1 represents cylindrical

chamber communicating with shaft below; 2, deep lip to prevent the

possibility of water passing into cylinder and down the shaft; 3,

curved plates to deflect and compress the air over outlet openings or

slits; 4, creates an induced current and exhausts the air from the

cylinder; 5, radial plates to deflect air off centre of slits; 6,

curved baffle plate or guard, to concentrate the current, and prevent

the wind blowing through the slits opposite. The downcast ventilator,

though necessarily more simple, is arranged, by means of similar

louvered webs to prevent any water passing below, lodging it on the

open deck instead. By means of up and downcast ventilators of this

type, it is possible to have the ventilation going on between decks

without interruption when there is a storm blowing and seas sweeping

the deck, whereas under ordinary conditions, and in similar weather,

everything would be battened down and the ventilation _nil_. The

inventors, of course, are able to point to other advantages possessed

by these ventilators, but the above are the salient features,

which have won for their system marked recognition and pretty wide

adoption. As evidencing its efficiency, it may be stated that Messrs

Boyle’s system was awarded the “Burt” prize of £50, offered for

international competition by the Shipwrights’ Coy. of London in 1882

for the best system of ship ventilation.

Having regard to the great importance of first providing means

whereby foul air may be extracted from compartments rather than first

attempting to put fresh air in—at least by other than mechanical

means—it has become the practice with several steamship companies

to fit a series of pipes from the rooms throughout the ’tween decks

all leading into a common main, carrying this main into the boiler

funnel, and thus utilising the powerful draught existing there when

the vessel is under way. The efficiency of this method is all that

could be wished, but its action is necessarily impaired when the

vessel is in port and the boilers not in use. For steamships having

long runs its value is very considerable; but in steamers having

short passages and long port delays its merits are not so pronounced,

and it is, of course, of no account when sailing ships are concerned.

Two systems of ventilation much alike in principle and equally

applicable to the steamer and sailing ship may be shortly referred

to. One is the Norton Ventilator, in which the dipping motion of

vessels is utilised in effecting their own ventilation; the action

in ocean-going vessels, of course, being continuous and automatic.

Two cylinders, closed at the upper ends, are placed on each side of

the stern post at such a distance as not to interfere in any way with

the action of the rudder, and sufficiently close under the stern to

be well out of harm’s way. As the vessel rises the water drops in

these cylinders, which are partly submerged, and in its fall causes a

vacuum, to fill which the air is drawn from all parts of the ship.

The sinking motion of the vessel again fills the cylinders and forces

the foul air collected, through the discharge pipes. The ventilator

admits also of being actuated by steam or other power on board

steamships, the exhausting and forcing device in this case consisting

of a water bell or air chamber to which a vertical reciprocating

motion is imparted by a beam or other attachment operated upon by the

mechanical power adopted. The other method referred to is that now

being pretty extensively introduced by Messrs Mosses and Mitchell, of

London. It consists of two small cylinders, placed on either side of

a ship, in-board, and connected by a pipe. The cylinders are partly

filled with water, and, as the vessel rolls, the water rushes from

the elevated to the depressed side of the ship, from one cylinder

to the other, and, by creating a vacuum, draws up the foul air from

between decks, or out of the hold, by pipes leading below. The air

which is pumped up by this self-acting process goes out through a

discharge pipe over the side, and such is the force of its exit that

it serves to blow a foghorn when required. The cylinders can be

placed so as to be worked by the pitching as well as the rolling of

the vessel, and there is always a sufficient movement of the water to

keep these pumps in action.

Systems of the other class—those involving the aid of mechanical

power—are as much available as the automatic systems, but the greater

expense of fitting, maintaining, and working them are considerations,

apart from the question of their greater efficiency, which stand in

the way of their general adoption. In vessels chiefly intended for

passenger or emigrant carrying, artificial ventilation by mechanical

means has been provided, and the practice is greatly on the increase,

but systems in which natural agents are more largely brought into

requisition have advantages which appeal most effectually to ship

owners in general.

In several modern steamships engaged in cargo and passenger service,

hydraulic machinery designed to take the place of the usual deck

steam equipment has recently been introduced with great advantage.

This embraces machinery used for steering the vessel, loading and

discharging cargo, heaving anchors; for performing, indeed, all the

work on board excepting that of propulsion. From experience of the

well proved utility and durability of hydraulic power on shore, it

seems quite a natural consequence that it should take its place on

board ship. Indeed, the system has so many advantages both from

the point of view of the passenger and of the steamship owner,

the wonder is that its introduction has been so long delayed. Its

perfect noiselessness, as compared with the rattling, hissing, steam

machinery now in vogue, is an advantage which will appeal strongly

to the sea voyager. The great speed of the system, as well as the

absence of jar and noise, the reduction in wear and tear, and the

obviating of well-known disadvantages incidental to steam pipes, are

merits of the system which are bound to appeal to the steamship owner.

It has been well pointed out by Mr A. Betts Brown, of Edinburgh, the

patentee and manufacturer of this class of machinery, in a paper read

by him before a recent meeting of the Institution of Naval Architects

that—“With all the noise of steam engines at work on deck, running at

piston speeds of as much as 1000 feet per minute, the cargo is lifted

from the hold at a rate of only from one to two feet per second,

which cannot be considered as keeping pace with the general progress

made in other departments of steamship economy. In short, vast sums

are spent on fuel to gain half a knot extra speed on a passage,

while hours may be wasted in port in consequence of the primitive

nature of the present system of deck machinery for discharging

cargo.” Previous to 1880, Mr Brown had supplied and fitted hydraulic

machinery on board the paddle-steamer _Cosmos_, built by Messrs A.

& J. Inglis, of Glasgow, intended for South American river service,

but it was only in that year that he had an opportunity of fitting a

large ocean-trading steamship with the system. This was the _Quetta_,

built by Messrs Denny, Dumbarton, to whom, with the managers of

the British India Association Steam Navigation Company, who own

the vessel, Mr Brown ascribes credit for the opportunity afforded

him of fitting his firm’s system on a complete scale. The _Quetta_

is 380-ft. in length, 40-ft. breadth, depth of hold 29-ft., and

3,302 tons gross, and is fitted with a complete system of hydraulic

machinery performing the following functions:—Steering, heaving the

anchor, warping by capstans fore and aft, taking in and discharging

cargo, lowering the derricks to clear cargo over side, hoisting

ashes, reversing main engines, and shutting tunnel water-tight

door in engine-room. For detailed descriptions of these various

appliances, the reader is referred to the before-mentioned paper.

The most for which space is here available is a very general outline

of the principle on which they are supplied with motive power. The

prime mover consists of a pair of compound surface-condensing pumping

engines of 100 indicated horse-power, situated in the engine-room

of the vessel. These engines pump water (or in winter non-freezing

fluid) from a tank into a steam accumulator. The pumping engines are

started and stopped by the falling or rising of the steam piston in

the accumulator; and since the piston falls when the hydraulic power

is being utilised, and rises to its former level when the power is

not in use, it follows that the apparatus is perfectly automatic.

Once started, it does not require the supervision of an engineer,

and it maintains a steady pressure of 800-lbs. per square inch in

the hydraulic mains or pressure pipes. These are carried up from

the engine-room, and extend fore and aft the ship. Alongside the

pressure main a similar return main is laid, which discharges into

the tank. From the pressure mains branches are connected to the

various hydraulic machines. After having done its work, the water

is discharged into the return mains, being thus used over and over

again. The experience obtained in the working of the _Quetta_ shows

that a donkey boiler of the usual size, just sufficient for steam

winches, enables the cargo to be discharged in half the time: in

other words, does double the work on a given coal consumpt with

compound surface-condensing pumping engine, and the hydraulic system.

The advantages of hydraulic machinery have been thus summarised:—A

pair of engines in one place do, with no noise and half the

consumption of fuel, the work usually performed by perhaps a dozen

donkey engines, while about £30 or £40 a voyage is saved in wear and

tear. The increase of speed obtained in loading and discharging cargo

practically ensures a quicker voyage. The rapidly working machinery

necessitates double gangs of men in the hold; but though the hands

are more numerous they are paid for a shorter time, and the cost of

labour per ton of cargo is thus less than usual. The prime outlay

is considerably greater than under the ordinary system, but it is

calculated that in at least three years the extra expense will have

been saved.

Notwithstanding the considerable increase in cost (more than double

that of steam equipment) of the hydraulic system, the British India

Association have seen their way to fit the succeeding steamers

they have built, similarly to the _Quetta_, namely, the _Bulimba_,

_Waroonga_, and _Manora_, the two intervening ships having their

emigrant quarters ventilated by fans driven by hydraulic engines, as

well as the usual deck equipment. In addition to the above, there

have already been nine other steamers fitted successfully by Mr

Brown’s firm with hydraulic machinery—including the Union Steamship

Coy.’s _Tartar_, of 4340 tons—and there is every prospect now of its

taking the place of the noisy steam machinery in at least our most

important passenger lines.

* * * * *

The regard which is had to comfort and luxury in modern passenger

steamers has manifested itself—like the attention devoted to

swiftness and safety—in various propositions and designs of a more

or less novel kind. These, indeed, have very often consisted of

designs embracing the whole of the qualities named; comfort and

luxury being coincident with the more important properties of speed

and safety already noticed; but not a few propositions and actual

undertakings have consisted of vessels in which comfort has largely

been the dominant and regulating condition of design. This subject

receives happier illustration from the history of steam service

between England and France, than perhaps from any other service

that could be instanced. The thought and speech expended on “an

efficient Channel service” at the meetings of the various societies

concerned with shipbuilding and marine engineering, and the space

devoted to the subject in the technical journals, has been no more

than commensurate with the number and variety of projects for its

accomplishment, submitted from time to time. Many of the schemes

have not been quite of a marine character, and these, of course,

lie beyond the province of the present review; but so far as ships

are concerned, it is interesting to note to what extent comfort has

been the dominant and regulating condition in the designs. In the

_Castalia_ and the _Calais-Douvres_, employed in Channel service,

features of considerable novelty—notably the double hulls—were

adopted, and it was to the desire for increased comfort as much as

speed that their introduction was owing.

In the steamer _Bessemer_, however, built at Hull in 1875, this

subject finds happiest illustration. This steamer, which involved

some very interesting and novel problems in shipbuilding—in which

the matters of propulsion and steering were largely concerned—was

designed for the special purpose of practically testing an invention

of Mr Henry Bessemer’s, having as its object the alleviation of the

evils of sea-sickness. Mr (now Sir Henry) Bessemer’s invention, as

applied in this case, consisted of a saloon supported on longitudinal

pivots, which was to be made unsusceptible to transverse oscillation

by the application to it of machinery wrought by hydraulic power. It

was the intention of the eminent inventor to have applied this system

to the correction of longitudinal as well as transverse oscillation,

but on considering that the steamer was to be of large dimensions

and performing a service in comparatively small waves it was thought

desirable to limit its application to transverse motion, at the same

time having regard to the longitudinal motion by reducing the height

of the vessel for a distance of 50-ft. at each end, thereby inducing

depression at the extremities, through the vessel’s not rising to,

but being overswept by, the waves.

Although an influential company was formed to work the _Bessemer_

and other vessels embodying her novel features, which it was thought

might follow, she was virtually abandoned after one or two trials

across the Channel. Her failure was assumed without exhaustive and

conclusive trials being made of the many novelties embodied in

her construction, some of which were obviously of an experimental

character. This is the more to be regretted because of the beneficent

issues involved in the project, and also in some degree because of

the extent to which the faith of some intrepid and experienced men

was pledged to its success. Nevertheless, it was always a matter of

grave doubt, even when the fullest measure of mechanical success was

allowed for, whether the idea of the pivoted saloon was calculated to

secure that immunity from the effects of ship motion in a seaway, for

which the celebrated patentee felt induced to hope.

It is maintained by many who profess to have given the subject

attention, that sea-sickness in its most virulent forms, and in the

majority of instances, is less attributable to the transverse and

longitudinal oscillations—known respectively, as the “rolling” and

“pitching” motions—than to the vertical movement termed “dipping,”

which in its descent from the summit of one wave until upborne by the

wave next following, the vessel undergoes. Now, this is a condition

for which, in the Bessemer project, there was no provision, nor

indeed well can be under any circumstances, save in the simple but

costly expedient of adding to the dimensions or bulk of vessels,

irrespective of form. The Czar of Russia’s yacht _Livadia_, built

some years ago, exemplified in her extraordinary dimensions and great

bulk the truth of such reasoning. The actual rolling and pitching of

this remarkable vessel, as observed in the height of a gale in the

Bay of Biscay, and in the midst of very heavy seas, was exceeding

small. This never exceeded four degrees for the single roll, or seven

degrees for the double roll, nor beyond five degrees for the forward

pitch, or nine degrees for the double pitch, so to speak. This

horizontal steadiness appeared to experts, who were on board at the

time, most remarkable, and Sir E. J. Reed, in a communication to the

_Times_, commented amongst other things on the agreeableness of the

contrast the voyage on the _Livadia_ afforded, with his experience of

voyaging at sea in ordinary ships.

After all, it must be acknowledged that attempts hitherto made to

obviate the evils of sea-sickness by novelty in design fall very

far short of attaining the beneficent results sought after. The

_Bessemer_, the _Livadia_, the _Calais-Douvres_, and other _unique_

craft primarily conceived with regard to this end, are now, it

would seem, exemplifying in their latter fate the futility of the

endeavour. Such attempts, however ill-advised they may possibly

appear in the light of the knowledge their very failure or their

partial successes yield, have still their creditable and praiseworthy

aspects. The spirit which has prompted some of them is not wholly

one of money-making, and their histories enrich the general fund of

experience far more than libraries of untried theories. Shipowners

are too ready to shut their minds against everything which seeks

the _acme_ of comfort and safety by other means than those which

guarantee _economical_ success, or those which consist in increasing

the size and power, and enhancing the accommodation of conventional

types of vessels. These novelties and innovations, on the other hand,

represent more of the intrepidity essential to genuine advancement

than is forthcoming in a thousand merchant ships of the conventional

type.

Happily the need for such enterprise as is involved in at once

departing from tried types, has within recent years been largely, if

not altogether, obviated, through improved procedure in the work of

design. The more thoroughly analytic process of investigation and

experiment now in vogue, greatly curtails the number of novelties

introduced, or which reach the constructive stage. Many present-day

projects never get beyond the “paper stage,” which in times not so

far distant would have spelled out “failure” to the very last letter.

Since the system of model experiment has begun to be practised in

a reliable manner, and since theoretical prediction generally has

become better appreciated, over-sanguine inventors have been spared

the penalties of failure in actual practice, and ingenuity has been

reclaimed or warned away from channels that would inevitably have

proved chimerical.

List of Papers bearing on the safety and comfort of modern

steamships, to which readers desiring fuller acquaintance with the

_technique_ and details of the subjects are referred:—

ON THE NECESSITY OF FITTING PASSENGER SHIPS WITH SUFFICIENT

WATERTIGHT BULKHEADS, by Mr Lawrance Hill: Trans. Inst. N.A., vol.

xiv., 1873.

ON WATER AND FIRE-TIGHT COMPARTMENTS IN SHIPS, by Mr Thomas May:

Trans. Inst. N.A., vol. xiv., 1873.

ON CAUSES OF UNSEAWORTHINESS IN MERCHANT STEAMERS, by Mr Benjamin

Martell: Trans. Inst. N.A., vol. xxi., 1880.

ON MODERN MERCHANT STEAMERS, by Mr James Dunn: Trans. Inst. Naval

Architects, vol. xxiii, 1882.

ON BULKHEADS, by Mr James Dunn: Trans. Inst. N.A., vol. xxiv., 1883.

ON PUMPING AND VENTILATING ARRANGEMENTS, by Mr Thomas Morley:

Trans. Inst. N.A., vol. xvii., 1876.

ON SIR WM. THOMSON’S NAVIGATIONAL SOUNDING MACHINE, by Mr P. M.

Swan: Trans. Inst. N.A., vol. xx., 1879.

ON STEAMSHIPS FOR THE CHANNEL SERVICE, by Mr John Grantham: Trans.

Inst. N.A., vol. xiv., 1873.

ON CHANNEL STEAMERS, by Mr John Dudgeon: Trans. Inst. N.A., vol.

xiv., 1873.

ON HIGH-SPEED CHANNEL STEAMERS, by Mr H. Bowlby Willson: Trans.

Inst. N.A., vol. xv., 1874.

ON THE ARK SALOON, OR THE UTILISATION OF DECKHOUSES FOR SAVING LIFE

IN SHIPWRECK, by Rev. W. R. Jolley, R.N.: Trans. Inst. N.A., vol.

xv., 1874.

ON THE BESSEMER STEAMSHIP, by Mr E. J. Reed: Trans. Inst. N.A.,

vol. xvi, 1875.

ON THE BESSEMER CHANNEL STEAMER: Naval Science, edited by Mr E. J.

Reed, 1873.

ON ELECTRIC LIGHTING FOR SHIPS AND MINES, by Mr Andw. Jamieson:

Trans. Inst. Engineers and Shipbuilders, vol. xxv., 1881-82.

ELECTRICITY ON THE STEAMSHIP (Series of Papers): the “Steamship,”

vol. I., 1883.

ON THE VENTILATION OF MERCHANT SHIPS, by Mr Jas. Webb: Trans. Inst.

N.A., vol, xxv., 1884.

ON THE COMPARATIVE SAFETY OF WELL-DECKED STEAMERS, by Mr Thos.

Phillips: Trans. Inst. N.A., vol. xxv., 1884.

ON THE APPLICATION OF HYDRAULIC MACHINERY TO THE LOADING,

DISCHARGING, STEERING, AND WORKING OF STEAMSHIPS, by Mr A. B.

Brown: Trans. Inst. N.A., vol. xxv., 1884.

CHAPTER IV.

PROGRESS IN THE SCIENCE OF SHIPBUILDING.

The appreciation and employment of scientific method and analysis in

designing and building ships have at no previous time been greater

than they are at present. This is already yielding benefits and

ensuring successes which only a few years ago would have remained

ungathered and unachieved, or at best would only have been attained

after wasteful expenditure of money, time, and skill, if not the

sacrifice of human life. Not so long ago endeavours were seldom made

to extract lessons of general value from particular occurrences,

there being a disposition prevalent to accept facts without

accounting for them—“to rejoice in a success and regard a failure as

irreparable”—the outcome, it may at once be said, of indifference,

false ideas of economy, and of a limited conception of the part

scientific methods should play in successful shipbuilding.

Particular occurrences within recent years have without doubt played

a large part in bringing about this more general and intelligent

appreciation of such matters. Some maintain, indeed, that it is

only under pressure of circumstances that anything like proper

regard for fundamental principles has obtained hold among mercantile

shipbuilders. This remissness, even admitting it to be true, is the

more natural and excusable in private commercial concerns, when it

is considered that the bulk of progress made, even in Admiralty

quarters—where ships take several years each to build, and there

is more time for scientific investigation and experiment than is

possible in mercantile work—is more attributable to the awakenings

which have followed upon great disasters than to the natural

improvement of ordinary practice. The terrible loss of the _Captain_

in September, 1870, for example, by which 500 lives were sacrificed,

led to a fuller recognition of the necessity for exact experiment

and calculation to determine thoroughly the conditions of stability

for war vessels; and many war-ships then under construction at the

dockyards—particularly those of the low freeboard type—were altered

in consequence, for the purpose of adding to their safety. The

capsizing of the _Eurydice_ off the Isle of Wight in March, 1878;

the mysterious and mournful loss of her sister ship the _Atalanta_

in 1880; the explosion on board the _Thunderer_ in 1876, by which 45

lives were lost, and the still more calamitous case of the _Doterel_

in April, 1881, by which the ship and 148 lives were destroyed,

are all instances of calamity, the causes of which have formed the

subject of official inquiry, all in their turn teaching important

lessons and yielding subsequent benefits not easily calculable.

Recent occurrences of a very calamitous nature in connection with

merchant ships—some of which will be more explicitly referred to

further on—have been attended with similarly mournful, but, it may

be added, with similarly beneficial results. These disasters and

the resulting inquiries have shown pretty conclusively that the

knowledge of a vessel’s stability and other vital qualities possessed

by ship’s officers is often meagre and erroneous; and that far too

little attention is usually paid to a vessel’s technical qualities

by shipowners or their advisers. They have also tended to prove that

exact knowledge of the principles of ship design, and observance of

scientific method in their construction, are not yet sufficiently

prevalent or thorough in mercantile shipyards.

* * * * *

Progress in the pure science of naval architecture, as distinguished

from the practical application of scientific rules and principles

to shipbuilding, is a great and complex subject, and one which it

would be impossible to do full justice to here. Before attempting

to treat upon these matters as concerned with the period covered by

this review, it may be instructive to trace briefly the progress

made in the past, and take note of the agencies through which such

progress has been effected. In this undertaking, concerned as it

is with matters relating to a period prior to that with which the

present work chiefly deals, the author has availed himself to some

extent of already published works traversing the same ground. As

having afforded the needful assistance in this connection, and as

being a source to which readers may turn for fuller information,

reference may here be made to an article in the _Westminster Review_

of January, 1881, on “The Progress of Shipbuilding in England.” This

article, though unsigned, is from the pen of Mr W. H. White, late

Chief Constructor of the Navy, and author of the well known “Manual

of Naval Architecture.” It furnishes an appreciative and concise

account of the literature and the educational agencies connected

with the theory of naval architecture, and sketches the influence of

science on practice, and _vice versa_ in the profession since the

beginning of the present century.

As has already been indicated, the period during which scientific

knowledge and methods have had any considerable place in merchant

shipbuilding, does not extend back over very many years. In

connection with the Royal Navy, however, the study of scientific

naval architecture has been fostered and promoted under Government

auspices almost from the commencement of the present century; not,

however—it must be added—without alternating periods of regard and

neglect, nor irrespective of pressure from extraneous sources.

Although progress in this matter has not been solely due to

Government agencies, it may be maintained that a large part of the

positive and accurate scientific knowledge which now exists has

grown out of the exigencies of the naval service, and has come from

sources more or less supported by or connected with Government

institutions. It will of course be understood that the science of

naval architecture is a field in which many besides shipbuilders,

and indeed many besides professional naval architects, have laboured

with signal success. The fund of knowledge has been enriched, and

the practice of shipbuilding improved, by men whose association

with the shipyard has been of an indirect and amateur kind, and—it

must be added—whose valuable labours the shipyard has often but

scantily recognised. Mathematicians—“mere theorists,” as they have

been called—have made original investigations and scientific analyses

which have upset many previously received practical notions, and

established principles, the appreciation of which alone, has led to

subsequent progress in actual practice. The part taken by merchant

shipbuilders has consisted in the experimental verification, and

sometimes the practical correction of principles thus evolved, but

even to this extent the service done has been largely incidental.

Those considerations which form the economic basis of every

commercial concern have naturally circumscribed such service, and

only a few notable firms have been able to break through the common

restrictions.

The systematic study of scientific naval architecture may be said

only to have begun in Britain in 1811, in which year, as the outcome

of recommendations made by a Government Commission appointed to

inquire into naval construction in 1806, the first School of Naval

Architecture was established at Portsmouth, under the direction of

Dr Inman, a distinguished member of the University of Cambridge. All

the great advances which had been made previously in the science

of naval architecture were chiefly due to foreigners, and any one

wishing to acquaint himself at first hand with all that was then

most advanced would have to consult the learned treatises of such

distinguished Frenchmen as Bouguer, Dupin, Euler, D’Alembert, and the

Abbé Bossut, of the distinguished Spaniard Don Juan d’Ulloa, and of

Chapman, the celebrated constructor of the Swedish Navy. One or two

English writers, between 1750 and 1800, had published translations

of some of these foreign treatises, but the only original work of

any importance was by Atwood, who contributed a “Disquisition on

the Stability of Ships” to the proceedings of the Royal Society

(1796-98). This contribution was both a criticism and an extension of

flotation and stability investigations by Bouguer, and as an example

of scientific method applied to exact calculations of the qualities

of ships it is still well worthy of study. In 1791 a “Society for the

Improvement of Naval Architecture” had been formed, the membership

being both numerous and influential, and in 1806 the growing sense of

need for improved scientific methods culminated in the appointment of

the Commission above mentioned, and in the establishment five years

later of the first School of Naval Architecture. This institution

existed for over twenty years, over forty students were trained, and

the science of naval architecture was greatly promoted through its

agency. Almost as a body the students of this school, with their

able teacher, deserve the honour of being regarded as the founders

of an English literature of naval architecture. Nevertheless, the

recognition of Dr Inman’s services, and his pupils’ capabilities as

designers, by the naval authorities was of a cold and disappointing

nature. Ultimately, however, many of them attained positions wherein

their talents found worthy exercise.

After the abolition of the School of Naval Architecture, under Dr

Inman, in 1832, no agency for higher education existed until 1848,

when the urgent necessity for a steam re-construction of the Navy

forced attention to the want of trained men, and resulted in the

establishment of a second school at Portsmouth. The principal of

this school was Dr Woolley, an eminent graduate of the University

of Cambridge. From 1848 on to the present time, Dr Woolley has

held a prominent place amongst the promoters of naval science, and

the pupils produced by the institution under his directorship have

given in various ways good practical evidence of his capability as a

teacher. After five or six years of useful work, this second school

was done away with, and a third was established in London in 1864,

after pressure had been brought to bear upon the Government of the

day by the Institution of Naval Architects—an association which was

founded in 1860, and which has since had so flourishing an existence.

The new school was placed for a time under the control of the

Science and Art Department at South Kensington, Dr Woolley being

Inspector-General, and the late Mr C. W. Merrifield, F.R.S.,

Principal. This school, unlike its predecessors, was not nominally a

mere Admiralty establishment, but offered admission to private naval

architects and engineers, and did not exclude foreigners. It remained

in operation at South Kensington until 1873, when the Admiralty

decided to establish the Royal Naval College at Greenwich, and to

train their students of naval architecture and marine engineering

there. Since 1873, therefore, what may be regarded as a continuation

of the third school has been at work at Greenwich, the Admiralty

granting facilities for the entry of private and foreign students,

much as was done at South Kensington.

The small extent to which this institution has been taken advantage

of by private students, or by those whose aim is to equip themselves

for service in merchant shipbuilding, notwithstanding the inducements

existing in the shape of substantial scholarships, has often been

subject of comment. Various reasons have been adduced for this state

of matters, but the true cause would seem to be largely concerned

with the character of the entrance examinations and with the course

of study provided. The subject is well worthy of consideration, and

fuller reference will be made to it further on when some educational

agencies which have been recently established are under consideration.

At such important junctures in the history of shipbuilding as the

introduction of steam power for propulsion in place of sails, and

the employment of iron in place of wood for the hulls, precedent

and experience lost much of their value under the new conditions.

The association of civil and mechanical engineers with shipbuilding

at these crises was of immense advantage. Such men as Fairbairn

and Brunel, who had previously gained high reputations in other

branches, were enabled by their scientific skill in designing bridges

and other structures in wrought-iron, to achieve much, and to take

the lead in ship design and construction. “To men of this class,”

says Mr W. H. White, in the article already alluded to, “careful

preliminary investigation and calculation naturally formed part

of the work of designing ships; ‘rule of thumb’ was not likely to

find favour, even if it had been applicable, which it was not, under

the circumstances. At first, much was done on imperfect methods,

comparatively in the dark; failures were not rare; yet progress was

made, and gradually greater precision was attained, in the attempt

to design steamers capable of proceeding at certain assigned speeds

when laden to a given draught. In fact, the construction of steamers

rendered imperative a careful study of the laws of fluid resistance,

and of the cognate investigation of the mechanical theory of

propulsion—both of which subjects lay practically outside the field

of the designers of sailing ships. The speed of a sailing ship is

obviously dependent upon the force and direction of the wind; her

designer, therefore, chooses forms and proportions which will enable

a good spread of canvas to be carried, on a handy stable vessel.

Questions of resistance to the progress of the ship were therefore

subordinated to sail-carrying power and handiness in sailing ships;

whereas in steamers designed for a certain speed the question of

resistance occupies a primary place, seeing that the engine power

must be proportioned to the resistance. Consequently, while keeping

in view stability, handiness, and structural strength, the designer

of a steamer has a more difficult task than the designer of a sailing

ship, and the difficulty can only be met if faced intelligently by

scientific analysis. Hence it happened, as was previously remarked,

that a more general appreciation of the value of scientific methods

accompanied the development of steam navigation and iron shipbuilding

in the British mercantile marine.”

Another name that must be linked with those already mentioned in

connection with the change from wood to iron in shipbuilding, and

with the new conditions imposed by the transition from sail to steam,

is that of the late Mr John Scott Russell, already referred to at the

beginning of this work. In the fields of inquiry so largely opened

up at the period referred to, Mr Russell was a most distinguished

worker. His advocacy and adoption in practice of special structural

principles, as illustrated not only in the _Great Eastern_ but in

other vessels, has influenced subsequent practice incalculably, and

by his persevering investigations upon the resistance of vessels,

and the “wave-line” theory he advanced, as well as by his inquiry

into the characteristics of wave motion, he laid designers of that

period and subsequent investigators under great indebtedness. His

contributions to the literature of the profession—notably his _magnum

opus_, entitled “Modern System of Naval Architecture”—and the large

share he subsequently took in the deliberations of the Institution of

Naval Architects, and of other societies concerned with shipbuilding

and engineering, enhance that indebtedness and remain as permanent

records of his skill and originality.

Approaching the period with which this review is more particularly

concerned, reference must now be made to the valuable labours of two

eminent men, whose loss the profession has had to mourn within recent

years. These are the late Professor Macquorn Rankine and the late Mr

William Froude, neither of whom was by profession a naval architect,

yet both of whom were led by love of the subject to give their

matured experience as civil engineers and mathematical experts to the

promotion of knowledge in this domain.

Rankine appears to have become specially interested in the problems

connected with ship design, after he became Professor of Civil

Engineering at Glasgow University in 1855. Conjointly with Mr Isaac

Watts, late Chief Constructor of the Navy, and formerly a student of

the first School of Naval Architecture; Mr F. K. Barnes, now Surveyor

of Dockyards, and Chief Constructor of the Navy, and a distinguished

student of the second school; and the late Mr J. R. Napier, a member

of the famous Clyde shipbuilding firm, Prof. Rankine produced in 1866

“Shipbuilding: Theoretical and Practical.” This valuable treatise was

edited, and for the most part written, by Prof. Rankine, and provides

a complete system of information on all branches of shipbuilding

and marine engineering, although subsequent progress in certain

departments of naval science has made a new edition desirable. The

work is also distinguished for its enunciation of several theories

connected with the resistance and propulsion of vessels by Prof.

Rankine, which have become the accepted basis of modern practice.

Of these the mechanical theory of the action of propellers, and

the stream-line theory of resistance, are the best known. His

investigations and writings on the latter subject were most ably

supplemented and confirmed by Mr Froude, whose beautifully-contrived

model experiments, coupled with his discovery of the law by which

such experiments can be made to afford reliable data for the

resistance of full-sized vessels, have laid the profession under even

a heavier load of indebtedness.

This, however, was not the only work of investigation and experiment

with which Mr Froude actively and inseparably identified himself.

Taking up a subject which many authorities before him had studied and

written upon with but little success—that of the phenomena of wave

motion and the oscillation of ships in a seaway—he propounded and

demonstrated at the Institution of Naval Architects in 1861, after

much careful thought and experiment, a theory with respect to it

which at that time was entirely new and striking, but which has since

been firmly established as the sound one.

At first, authorities in the science of naval architecture, like

Moseley and Dr Woolley, regarded the new theory with suspicion and

disapproval; Rankine, on the contrary, warmly supported it, and

helped to develop it and to answer various objections urged against

the hypothesis on which it was based. For nearly twenty years

Mr Froude steadily pursued the inquiry, adding one mathematical

investigation to another, carrying out numerous experiments, and

making voyages for the purpose of studying the behaviour of ships.

Broadly speaking, it may be said that whereas earlier investigations

gave to the naval architect the power of making estimates of the

buoyancy and stability of ships floating in smooth water, they gave

up as altogether hopeless the attempt to predict the behaviour of

ships at sea, or to determine the causes which produce heavy rolling.

On the other hand, thanks to Mr Froude, the designer of a ship now

knows what precautions to take in order to promote steadiness and

good behaviour at sea.

Although the propositions enunciated by Mr Froude were accepted

as laws in a wonderfully short time—considering their startling

nature—their influence on practice, and especially the practical

application of the methods of comparison by which they had been

established, have not even yet been brought to anything like their

full issue. The work is being continued upon the lines laid down

by Mr Froude, amongst others by men whose closer intimacy with the

actual affairs of the shipbuilding yard may be expected to yield

results which will be more immediately reflected in actual practice.

Passing allusion has already been made to the founding of the

Institution of Naval Architects, but an association which has

gathered into its membership so largely of all sections of men

concerned with shipbuilding and shipping, and absorbs so much of the

knowledge and talent in these domains, must have fuller reference

made to it. Regarding its foundation, in 1860, Mr White, in his

article in the _Westminster Review_, says:

“The scheme of the Institution was happily conceived and well

executed. Amongst its earliest members were found the trained naval

architects of the first and second Schools, the leading private

shipbuilders and marine engineers, the principal shipbuilding

officers of the Dockyards, men of science specially interested in

naval architecture, shipowners, merchants, and others connected

with shipping; while a considerable number of sailors from the

Royal Navy and Mercantile Marine showed their appreciation of the

value of naval science by becoming Associates. The list of names

is eminently representative. Sir John Pakington (afterwards Lord

Hampton), then only recently retired from the office of First

Lord of the Admiralty, was the first President. Many experienced

naval officers supported him. There were men like Watts, Read,

and Moorsom, who had been pupils of Dr Inman half a century

before; others, like Fairbairn, Laird, and Grantham, who had been

conversant with iron shipbuilding from its commencement; marine

engineering was worthily represented by veterans like Penn,

Maudslay, and Lloyd; mathematicians and men of science like Canon

Moseley, Dr Woolley, Professor Airy, and Mr Froude appear on the

list. Private shipbuilders and naval architects like Scott Russell,

Samuda, Napier, and White, joined in the movement, so did the

surveying staff of Lloyd’s Register. In fact, there was a general

appreciation of the endeavour to establish an association which

should enable all classes interested in shipping to interchange

ideas and experience with a view to general improvement. Mr Reed

was the first Secretary, retaining that post until he was appointed

Chief Constructor of the Navy, and in that position did much to aid

the progress of the Institution.”

While it is true that the membership list of the Institution in its

early days was of the representative character above indicated, it

should be pointed out that the actual proceedings of the Institution

were not shared in by anything like the variety of talent which the

list comprised, or which now distinguishes its annual meetings.

For many years it was almost the exclusive conference of Admiralty

authorities and members of those shipbuilding and engineering firms

who undertook Government work, and the transactions for a long time

were very largely confined to purely naval matters. The scientific

value of the earlier volumes of the transactions would certainly have

suffered considerably if the papers by Mr Froude and Prof. Rankine

had not formed contributions, and the prosperity and development

of the Institution would have been equally lessened had there not

been general infusion of “new blood” from the mercantile marine in

all parts of the country. This has been going on during the past

twelve years or more, and the scope and utility of the Institution’s

proceedings have increased with the change. Of the later development

of the Institution, the authority already quoted says:—

“Owing to the rapid advances constantly being made in both the

science and the practice of the profession, the ‘Transactions’ have

come to be the chief text-books available. Members and Associates

have joined from all the great maritime nations. Members of the

professional corps of naval architects and engineers of France,

Austria, Italy, Germany, the United States, Russia, Sweden, Norway,

Denmark, Holland, are proud to be numbered with their English

professional brethren, and not a few of these foreign members have

contributed valuable Papers. The meetings of the Institution afford

exceptional opportunities for the discussion of questions having

general interest, as well as others having more special value to

professional men. Different views of the same subject find capable

exponents, and lead to valuable discussions. The latest systems of

construction and most recent changes in _materiel_ are described by

competent authorities. Valuable _data_ are put on record relating

to the designs and performances of war-ships and merchant-ships.

Inventions of various kinds are described and examined. Abstruse

theoretical investigations are by no means rare; and, in many

cases, the contribution of one such Paper by an original thinker

has given a start to others and led to important extensions of

knowledge. In fact, the Institution of Naval Architects has

admirably fulfilled the intentions of its founders, acting as a

centre where valuable information could be collected, and whence

it could be distributed for the general benefit of the profession.

Before it was founded naval science had no home in England; its

treasures lay scattered far and wide in occasional Memoirs and

Papers; but now everything worth preservation naturally finds

its way to the ‘Transactions.’ Any movement affecting shipping

also leaves its record there in Papers and Discussions which will

hereafter have a high historical value.”

As evidencing the change which has latterly come over the Institution

with respect to its annual proceedings, it may be noted that whereas

in the early years there were at some meetings no papers—leaving out

of account those by Froude and Rankine—except by Admiralty members

and others concerned with Government work, there was not a single

paper by an Admiralty man during the meetings of the present year.

* * * * *

With the general reference already made to Mr Froude’s invaluable

labours in connection with the resistance of vessels the brief

statement of the agencies through which progress has been made during

the present century may be considered as brought down to the period

coming within the scope of the term “Modern,” as used in this work.

The more difficult task of chronicling the progress made during the

period in question, both in the science of naval architecture purely,

and in the application of science to practice, must now be attempted.

The plan upon which it is proposed to accomplish this is to show

wherein and to what extent scientific methods in designing and

observing the behaviour of ships have been regarded, and indicating

generally where still further improvement may be looked for. To

accomplish this in such a way as to take appreciative account of the

most salient features, and yet to avoid difficult technical terms

and unnecessary elaboration, may involve some omissions and slight

inaccuracies, important enough from a strictly scientific point of

view, yet which do not materially affect the faithfulness of the

record.[5]

As preparing the way for references to those more special points in

connection with which scientific progress has taken place during

recent years, the following general and elementary outlines of the

principal scientific problems in ship design and construction may be

helpful to many readers:—

DISPLACEMENT AND CARRYING CAPABILITY.

A vessel floating at rest displaces a volume of water whose weight

equals her own total weight.

For vessels floating in sea water the number of cubic feet of water

displaced per ton of weight is, as nearly as possible, thirty-five.

For vessels in fresh water—_i.e._, lakes or rivers—the cubic feet

per ton of weight is thirty-six.

By calculating the volume of under-water portion of the vessel’s

hull, the number of cubic feet displaced by the vessel when

floating at any given draught is obtained. This result, divided by

35 or 36, according as the water is salt or fresh, gives the number

of tons weight displaced, and consequently the total weight of the

vessel.

Calculations being made of the volume of the vessel’s hull to

intermediate distances between the keel and the maximum load line,

it is thus possible to construct a “curve of displacement” from

which the actual amount of displacement at any intermediate draught

can be obtained.

From this curve a set of scales—usually set up alongside a

vertical scale of feet and inches, representing the vessel’s

draught-marks—are constructed, showing—1st, the tons “displacement”

at any draught; 2nd, the tons of “dead-weight” capability—_i.e._,

the tons displacement due to the weight of cargo, coal, ballast,

stores, fresh water, spare gear, &c.—at any draught above the

vessel’s light-draught: “light-draught” being that at which the

vessel floats with holds clean-swept, bilges dry, water in boilers,

and with such spare gear on board as is required by Board of Trade;

and 3rd, the amount of “freeboard”—_i.e._, the distance in feet

and inches from any particular draught line to the top of the deck

amidships.

BUOYANCY AND STABILITY.

A ship floating upright and at rest in still water must fulfil two

conditions—1st, as stated above, she must displace, a weight of

water equal to her own weight; 2nd, her centre of gravity must lie

in the same vertical line with the centre of gravity of the volume

of displacement or “centre of buoyancy.”

The whole weight of the ship may be supposed to be concentrated at

her centre of gravity, and to act vertically downwards, and the

resultant vertical pressure of the surrounding water in the same

way to act upwards through the centre of buoyancy.

When the ship has been inclined from the upright position, by any

force, the downward and the upward forces—weight and buoyancy

respectively—act through two separate but parallel vertical

lines, and form what is technically known as a “couple.” The

perpendicular distance between the vertical lines usually varies

with the inclination, and is called the “arm” of the couple. This

arm measures the leverage with which the weight and buoyancy of the

ship tend either to force her back into the upright position, or

to incline her still further, and, it may be, to capsize her. The

former effect would be the result of what is known as a “righting

couple,” the latter the result of an “upsetting couple.”

[Illustration: FIG. 14. FIG. 15.]

This may be made clearer by illustration. On Figs. 14 and 15,

which show in outline a vessel’s midship section, the vessel being

inclined to a small angle, =G= represents the centre of gravity

of vessel, and =B= the centre of buoyancy. The water line =W.L.=

corresponding to the upright position, in the inclined position

becomes =W_{1}.L_{1}.=, and the centre of buoyancy =B= shifts out

on the immersed side of the vessel to =B_{1}=. Assuming in the case

of Fig. 14 that some external force not involving any shifting of

the centre of gravity has produced the inclination, then the weight

of the vessel acts downwards through =G=, and the buoyancy of her

displacement acts upwards through =B_{1}=, as indicated by the

arrows passing through these points. The combined effect of these

forces, in this case, is to rotate the vessel towards the upright,

_i.e._, it forms a “righting couple.” Fig. 15 illustrates a case

of the opposite kind. The angle of inclination may be supposed to

be greater than in Fig. 14, and the centre of gravity =G= is much

higher in the vessel. The vertical through =B_{1}= is to the left

instead of to the right of the vertical through =G=. The effect of

the forces in this case is to rotate the vessel in the direction

of inclining her still further, and to capsize her—_i.e._, it

forms an “upsetting couple.” A line at =G=, therefore (Fig. 14),

taken at right angles to the new vertical line, gives the distance

which corresponds to the righting arm (=G= =Z=). A similar line at

=G= (Fig. 15) represents the upsetting arm. The lengths of these

arms when multiplied into the displacement, gives the “moments” at

the respective degrees of inclination. The “curve of stability”

for a vessel is simply a graphic representation of these arms or

moments. When calculated for the various degrees of inclination,

they are set off as ordinates along a base line—the righting arms

or moments above, and the upsetting arms or moments below, the

line—at distances corresponding to the number of degrees in the

respective inclinations. A curve drawn through the extremities of

these ordinates is the curve of stability.

The two points above named whose relative positions are vitally

concerned with this subject—_i.e._, centre of buoyancy and

centre of gravity—are determined by shipbuilders for many of

their vessels, although the stability may not be calculated

to its full extent. The position of the centre of buoyancy is

easily ascertained from, and in fact usually forms part of, the

displacement calculation. While the position of centre of gravity

may be found by means of calculation alone, _i.e._—by the process

of estimating the position of the centre of gravity of each of

the component parts, and from this deducing the common centre of

gravity of the whole ship—the work is so laborious, complex, and so

liable to error, that it is scarcely ever adopted at the present

day by mercantile shipbuilders. The position can be ascertained

with comparative ease and greater accuracy by means of “inclining”

experiments with the finished vessel, or closely estimated

before-hand by means of data obtained in the manner alluded to from

previous vessels of similar type.[6]

Another point concerned with stability is that termed the

“metacentre,” which is found by calculation from the lines of

the vessel. Referring to Fig. 14, a vertical line drawn through

the centre of buoyancy =B_{1}= cuts the original vertical line

at =M=. The intersection =M=, when the vessel is inclined to an

indefinitely small angle, is the “metacentre.” It is approximately

the same in all ordinary vessels for inclinations less than say

10°, but varies with greater inclinations. The corresponding

intersections of the consecutive vertical lines for all degrees

of inclination are embraced in the term “metacentrique.” These

features in stability investigations were originated by Bouguer, to

whom reference has already been made. The manner in which they are

concerned with stability will be indicated further on. (See also

footnote on preceding page.)

RESISTANCE POWER AND SPEED.

A ship, in moving through the water, experiences resistance due to

a combination of causes, which combination, according to modern

accepted theory, is made up of three principal elements.

1st—“Frictional” or “skin friction” resistance, due to the

particles of water rubbing against the ship’s hull;

2nd—“Eddy-making” resistance, due to local disturbances or eddies

amongst the particles of water—almost wholly at stern of ship;

3rd—Surface disturbance of the water by the passage of the ship,

resulting in the creation and maintenance of waves: known as

“wave-making” resistance.

The conditions which govern each of these elements, and their

relative importance, may be generally indicated.

Surface-friction resistance, especially for vessels moving at

moderate or slow speeds, is much greater than the resistance due

to other causes—that is if the hull is ordinarily well formed. Its

amount depends upon the area of the immersed surface, upon its

length, upon its degree of roughness, and upon the velocity with

which the water glides over it—_i.e._, upon the speed of the vessel.

Eddy-making resistance only acquires importance in exceptional

cases, _e.g._, in ships having unusually full sterns. In ordinary

well-formed ships it is of small amount, and is caused mainly by

blunt projections such as shaft tubes, propeller brackets, and

stern-posts.

Wave-making resistance is much more variable than surface-friction

resistance. Its amount depends on the form and proportions of

vessels, and on the speed at which they move: being greatest, of

course, in ships of full form and in those moving at high speeds.

The sum of these three main elements of resistance constitutes the

total resistance experienced by a vessel if “towed” through the

water, that is, the resistance considered apart from the action or

influence of the propelling instrument. In the case of a steamship,

however, propelled by a screw or paddle-wheels, the resistance

is augmented, more or less considerably, according to the form,

surface, and disposition of the propelling instrument.

By the employment of various formulæ deduced by scientific

authorities from theory and experiment, an approximation can be

made before-hand to the total resistance of a proposed vessel,

and from this an estimate of the power required to drive her at a

certain speed. Moreover, through the law of comparison propounded

by Mr Froude, the resistance of a ship can at all times be deduced

with fair accuracy from the resistance of her model, certain

corrections well determined by experiment having to be made.

The power of marine engines is expressed either in “nominal” or

“indicated” horse-power. Nominal horse-power is a term practically

obsolete so far as being a measure of the efficiency of engines,

and only exists as a conventional method of commercially measuring

the sizes of engines. Indicated horse-power measures the work

done by the steam in the cylinders during a unit of time, and

33,000 units of work per minute, or 550 units of work per second,

constitute one horse-power. The effective mean pressure of

the steam is ascertained from diagrams drawn by means of the

instrument known as the “Steam Engine Indicator,” and hence the

term “indicated” horse-power.

The development by a vessel’s engines of the power requisite to

drive her at a certain speed is always very considerably more

than the power required simply to overcome her total resistance

at that speed. This excess of power developed over power usefully

employed in overcoming resistance is known as “waste work.” It

amounts in many cases to as much as from 50 to 60 per cent. of the

gross indicated power, and it is absorbed mainly as follows:—In

overcoming frictional and other resistances of the engines and

shafting, working air pumps, &c., and in overcoming the frictional

and edgeways resistance of the propeller. The residue of power

usefully employed is known as the ‘effective’ horse-power. The

respective causes of ‘waste’ and their relative amounts are

problems constantly demanding solution. Progressive speed trials

with actual vessels and experiments with small scale models are

daily contributing to their solution, and to some extent to their

reduction.

STRUCTURAL STRENGTH.

Considering a ship as floating in a state of rest in still water,

the volume of displacement represents a weight of water equal to

the weight of the ship. This equality, however, does not exist

evenly throughout the length of the vessel, or for individual

portions: thus, amidships the weight of water displaced by a

given length—in other words, the buoyancy—is usually considerably

in excess of the weight of that portion of the vessel and her

contents. Similarly at the extremities the ‘weight’ of a certain

length exceeds the ‘buoyancy.’ Between the part or parts of the

vessel in which there is excess of buoyancy over weight, and the

part or parts in which the weight exceeds the buoyancy, there must

obviously be sections of the ship at which the two are equal, and

these are termed “water borne” sections. A ship circumstanced as

described is in a condition similar to that of a beam supported

at the middle and loaded at each end. Such a beam tends to become

curved, the ends dropping relatively to the middle, and the ends of

the ship tend to drop similarly, the change of form being called

“hogging.” On the other hand, if the excess of buoyancy occurred

at the extremities and that of weight amidship, the ship would

resemble a beam supported at the ends and loaded at the middle. In

such a condition the middle would tend to drop relatively to the

ends: a change of form called “sagging.”

These general principles are much more readily and safely

applicable to ships while floating in ‘still water’ than to ships

when at sea—the strains experienced then being necessarily the

results of far more complex and severe influences. The existence of

waves and their rapid motions relatively to that of the vessel, and

the pitching, heaving, and other movements thus caused, increase

the inequality of distribution of weight and buoyancy and affect

more materially the strains brought upon vessels. Consideration of

the problem, therefore, involves a study of waves, both as to their

formation and action, and necessarily leads to a mode of treatment

which cannot have accurate regard for particular cases. Variable

influences of immense importance are also constituted by the state

of loading in vessels for merchant service. For a uniform basis of

comparison in these calculations such vessels are usually assumed

as loaded with homogeneous cargo—_i.e._, cargoes of equal density

throughout.

This fundamental element of relative ‘weight’ and ‘buoyancy’ having

been indicated, the chief strains to which a ship is subjected may

now be stated. This may be done with sufficient regard to general

accuracy, under four heads:—[7]

(1) Strains tending to produce longitudinal bending—“hogging” or

“sagging”—in the structure considered as a whole.

(2) Strains tending to alter the transverse form of a ship,

_i.e._, to change the form of athwartship sections.

(3) Strains incidental to propulsion by steam or sails.

(4) Strains affecting particular parts of a ship, or “local

strains”—tending to produce local damage or change of form

independently of changes in the structure considered as a whole.

To these might be added various other strains, which, however,

are of less practical importance, and are not felt in any

great degree—except in very special cases and under unusual

circumstances—apart from the strains which affect the structure

considered as a whole. The provisions made for the latter are,

under ordinary circumstances, sufficient to cover the demands of

the former, but particular cases may have to be provided for on

their merits, apart from the treatment generally applicable.

The manner of ascertaining the strength of a ship to resist

strains tending to produce longitudinal bending, is to compute

the effective sectional area of all the longitudinal items in the

structure which are brought under compressive or tensile strain,

and from this to calculate the strength in the same manner as for

a girder having an aggregate sectional area and a disposition of

material equivalent to that of the ship.

To ascertain the accurate maximum strains tending to produce

longitudinal bending, or, in excessive cases, to break the ship

across at the transverse section where the strains reach their

maximum, involves a careful and most laborious consideration of

the relative weight and buoyancy of individual sections throughout

the length, and is a task not generally undertaken in mercantile

shipyards.[8]

References to the nature of the transverse and other strains above

enumerated and the extent to which they have been investigated will

be made further on.

With regard to such fundamental properties of vessels as

displacement, weight, and carrying capability, nothing new has

for a long period been added to the fund of scientific knowledge.

One of the conditions now most commonly laid down by the owners

of a proposed ship is that which provides for a certain carrying

capability on a given draught of water and at a certain speed,

the principal dimensions of the vessel also being stipulated. The

problem of determining what total displacement will be required,

involves consideration and an estimate of—1st, The total weight of

hull having regard to structural strength; 2nd, the total weight of

machinery having regard to speed required. By using “co-efficients”

deduced from the weights of vessels of similar type already built,[9]

these are determined; and adding them to the carrying capability

or dead-weight stipulated, the required displacement can be closely

approximated to. For vessels of abnormal proportions or of very

unusual construction careful and detailed calculations of the weight

of materials are undertaken previous to tendering for them. In some

yards, indeed, a like degree of care is observed in ordinary cases:

methods of approximation involving the use of co-efficients such as

that based on cubic capacity being distrusted.

The further problem of determining what form of hull will give the

required displacement is the essential and all-embracing feature of

the work of design, as it involves consideration of almost all other

properties. The methods of designing ships are various, and a very

common method, at one time more followed than it now is, consists

in shaping a block model direct, and from it taking the necessary

measurements for displacement, and for full-size delineation in

the moulding loft. The disadvantages pertaining to this somewhat

antiquated method are becoming more recognised as shortened and exact

methods of linear or “draught plan” design are put forward.

Unless the plan of lines of a similar vessel of nearly the same

dimensions is at hand, the design of a new vessel is in many

instances done without previous calculation being made to ensure at

once obtaining the desired displacement. Special methods of quickly

arriving at this result are, however, not uncommon in mercantile

shipyards, and generally speaking the chief draughtsmen in the employ

of large firms doing a varied class of work have rules derived

from long experience, though not perhaps definitely systematised,

by which they are guided.[10] Irrespective of all such special

methods, however, the work of designing is now greatly shortened and

simplified by means of Amsler’s “planimeter,” an ingenious instrument

for measuring areas now becoming well known.[11] By employing the

instrument in question, the draughtsman need not too laboriously

strive after the exact displacement at first, as the time occupied

in ascertaining what displacement any set of lines gives, and in the

consequent fining or filling out, is very considerably less than by

the ordinary methods.

* * * * *

The question of stability, which has next to be considered, is one

of great difficulty and intricacy, and it was not till the middle of

last century that some of the principles upon which it depends began

to be understood. Bouguer showed in 1746 that the position of the

“metacentre” limits the height to which the centre of gravity of a

floating body may be raised without making it unstable, and that the

righting moments at small angles of inclination from a position of

stable equilibrium are proportional to the height of the metacentre

above the centre of gravity. As the position of the metacentre for

any given draught of water is easily determinable when once the

volume of displacement and the centre of buoyancy at that draught

have been ascertained, it has been the practice for a very long time

to construct a curve representing the height of the metacentre at

all draughts, and to use it for showing the limits above which the

centre of gravity cannot be raised with due regard to the stability

required for the practical working of vessels and for purposes of

safety: By the method of “inclining” vessels, already described (see

outline of fundamental principles, page 98), the determination of the

precise position of the centre of gravity is rendered comparatively

simple.[12]

While the vertical distance between the centre of gravity and the

metacentre—commonly termed the “metacentric height”—forms a measure

of the “initial stability,” or the stability at very small angles of

inclination, it is imperfect by itself, and may be very misleading

as regards the stability at larger angles. This was conclusively

demonstrated by Atwood in his papers read before the Royal Society

in 1796 and 1798, while other grounds for discrediting the standard

of stability furnished by mere metacentric height were discovered

subsequently, and have been signally emphasised, with additional

reasons, by recent occurrences. Atwood, in the papers referred to,

laid down a general theorem for determining the righting moments

at any required angles of inclination possessed by a ship having a

given draught of water and a fixed height of centre of gravity, the

principle of which involved the use of the moments of the volumes

of the “Wedges,” _i.e._, those parts of a vessel (see =W O W_{1}=,

=L_{1} O L=, fig. 15), which become immersed and emerged as she

is inclined. Several methods of simplifying Atwood’s calculations had

been devised previous to 1861,[13] but in that year Mr F. K. Barnes,

in a paper read before the Institution of Naval Architects, described

a method of accomplishing this which until within recent years has

been the one ordinarily adopted in computing the stability of a

vessel at various angles of inclination.[14]

Owing to questions having arisen at the Admiralty in 1867 respecting

the stability of some low freeboard monitors at very large angles

of inclination, Sir E. J. Reed, then Chief Constructor, directed

the matter to be investigated. The work was placed in the hands of

Mr William John, who embodied for the first time the results of the

calculations in the form of a curve of stability, which exhibited

the variations of righting moments with angles of inclination up to

the particular angle at which stability vanished. The entire range

of a vessel’s stability was thus made evident, and in such a form

as enabled the general problem to be far more comprehensively and

accurately treated than before. The results of Mr John’s labours were

described in a paper read by Sir E. J. Reed before the Institution of

Naval Architects in 1868, and a further paper, containing an improved

method of applying Atwood’s theorem to the calculation of stability

upon this extended scale, was read before the same Institution by

Messrs John and W. H. White in 1871. The loss of H.M.S. _Captain_,

in 1870, as already pointed out near the beginning of this chapter,

occasioned an immediate and serious regard for the stability of war

vessels. This disaster, with other losses at sea from instability,

also forcibly directed the attention of mercantile naval architects

to the subject, and investigations on the same complete scale as

those undertaken in the Admiralty have for some years been adopted in

a few leading mercantile shipyards.

In this way the peculiar dangers attaching to low freeboard,

especially when associated with a high centre of gravity, have been

pretty fully made known, but the character of the stability which

is often to be found associated with very light draught appears to

have escaped the attention it demands. Light draught is often as

unfavourable to stability as low freeboard, and in some cases more so.

These truths were forced into prominence at the inquiry held by Sir

E. J. Reed on behalf of the Government into the disaster which befell

the _Daphne_, a screw-steamer of 460 tons gross register, which

capsized in the middle of the Clyde immediately on being launched

from the yard of the builders, Messrs Alexander Stephen & Sons,

Linthouse, on July 3rd, 1883. Sir E. J. Reed, in his exhaustive

report, published in August, 1883, emphasised the lessons adduced at

the inquiry as to the peculiar dangers attaching to light-draught

stability; and Mr Francis Elgar, (now Professor of Naval Architecture

in Glasgow University), who was employed to make investigations

respecting the stability possessed by the _Daphne_ at the time of the

disaster, did much to guide consideration of the subject into this

channel. In a letter to the _Times_ on 1st September, 1883, Mr Elgar,

by way of explaining portions of his evidence at the inquiry, called

attention to the relation which exists between the righting moments

at deep and light draughts in certain elementary forms of floating

bodies, his communication throwing further light on the subject of

light-draught stability. It appears that the fundamental proposition

which underlies the variations in the stability of a floating

body with draught of water had never before been demonstrated or

enunciated.

It will be readily understood that a curve of stability for a

given draught of water and position of centre of gravity ceases to be

applicable if changes are made in the weight and consequent draught

of water of a ship or the position of the centre of gravity, or in

both. Now in mercantile steamers, from the extremely light condition

in which they are launched to the uncertain loaded condition of their

daily service as cargo-carriers, the variation of draught is very

considerable, and imports into the subject considerations which do

not obtain to any great extent in war ships.

To complete the representation of stability as it should be known

for merchant ships, it is now recognised that curves showing the

stability at every possible draught of water and for different

positions of centre of gravity should be constructed. By means of

“cross-curves” of stability, or curves representing the variation

of righting moment, with draught of water at fixed angles of

inclination, this comprehensive want can be met with something like

the necessary expedition. From such curves it is a simple operation,

involving no calculation save measurement, to construct curves of

the ordinary description, showing the righting moment at all angles

for any fixed draught of water and position of centre of gravity.

Professor Elgar was the first to publicly direct attention to this

valuable development of stability investigation of merchant ships,

doing so in an able paper “On the Variation of Stability with Draught

of Water in Ships,” read before the Royal Society on March 13th of

the present year. Simultaneously with Prof. Elgar’s employment of

such curves in actual practice their use had been independently

instituted by Mr William Denny in his firm’s drawing office, and the

mode in which they were worked out in this case was communicated in

a paper read by Mr Denny in April of the present year before the

Institution of Naval Architects.[15] Several important improvements

with respect to simplifying and shortening calculation distinguish

the method employed by Mr Denny, and that gentleman, in the paper

referred to, accords individual credit to members of the scientific

staff in his firm’s employ, who, on being entrusted with the work

of calculation, brought considerable originality to bear upon their

labours. The cross-curves described by Prof. Elgar were constructed

from a series of curves of stability calculated in the ordinary way.

This, however (as pointed out in an after-note to that gentleman’s

Royal Society paper), is less simple and very much less expeditious

than the method carried out under Mr Denny, which consists in

calculating the cross-curves directly by applying Amsler’s mechanical

integrator[16] to the under-water portion of the ship instead of to

the wedges of immersion and emersion, thus determining at once the

positions of the vertical lines through the centres of buoyancy at

the required angles of inclination. As thus carried out a complete

set of cross-curves can be produced with about one-third the labour

involved in employing the older method. The ease and rapidity with

which ordinary curves for separate draughts can be taken from

cross-curves has already been commented upon.

Many other investigators besides those already mentioned have

recently been working at the subject of stability, and a

considerable number have read papers, dealing with the extension and

simplification of stability calculations, before one or other of the

scientific societies concerned with naval architecture, most of the

methods put forward being well worthy of study.[17] To very many

shipbuilders, however, and to others besides them responsible for

the stability of ships, processes of arithmetical calculation—even

allowing for all the simplification which mathematical skill has

recently effected—appear still to be too intricate, or to absorb too

much time for their being entirely followed. As a simple means of

readily, although approximately, arriving at the results attained

more elaborately and reliably by calculation, attention has recently

been directed to an experimental process by which a complete curve

of stability may be constructed almost without the use of a single

figure! The method was first brought forward in 1873 by Capt. H. A.

Blom, chief constructor of the Norwegian Navy, formerly a student of

the South Kensington School of Naval Architecture, who described it

to the United Service Institution. The method has been employed by

shipbuilding firms on the Tyne and Clyde when a curve of stability

had to be produced in a very limited time, and when extreme accuracy

was not a desideratum. As practised by the firms in question, the

_modus operandi_ differs in some slight respects from that described

by Captain Blom, but the changes in no way affect the principles as

first laid down by him. The modern mode of procedure may be briefly

described:—

From the body plan of the ship, _i.e._, that portion of the draught

plan representing the vessel’s form by a series of equidistant

transverse sections—any convenient number of sections lip to the

load water-line are pricked upon and then cut out of a sheet of

drawing paper of uniform thickness. These sections are then gummed

together in their correct relative positions, care being taken

to spread the gum thinly and evenly. This paper model—greatly

foreshortened, of course—represents the immersed portion of the

ship (in other words, the displacement) when she is floating

upright. By suspending this model from two different points, and

taking the intersection of two vertical lines through the points of

suspension—or better still, by balancing it horizontally on a pin

and fixing the point when the model is in equilibrium—the centre

of gravity of the model, or in other words, the actual centre of

buoyancy is obtained.

Water lines at various angles of inclination are then drawn on

the body plan, all intersecting the water line for the upright

condition at the centre line of ship. The displacement represented

by the inclined water lines thus drawn, generally not being equal

to that for the upright position, a correcting layer has to be

added or subtracted for each inclination, in order to obtain this

end. By employing the planimeter the necessary thickness of this

layer can be most readily ascertained. Where a planimeter is not

available the actual floating line may be obtained, after the model

has been made, by cutting off layers, allowance having been made

for this purpose. The same number of sections as before are then

cut out to each of the inclined corrected water-lines, the paper

model prepared and the centre of buoyancy obtained as already

described.

Through this new centre of buoyancy a line is drawn perpendicular

to the inclined water line, and the distance between this line

and the centre of gravity of the ship, already obtained, is the

righting arm. If this process is repeated for each angle of

inclination, it is thus seen a complete curve of stability may be

approximately obtained.

[Illustration: FIG. 16. MODEL IN UPRIGHT POSITION ]

[Illustration: FIG. 17. MODEL IN INCLINED POSITION]

A further method of arriving at results by experiment, involving

principles not unlike those of the “paper section” method just

described, has recently come under the author’s notice, and through

the courtesy of its inventor—Mr John H. Heck, of Lloyd’s surveying

staff at Newcastle—the following general description of the apparatus

and fundamental principles is made public for the first time:—

By means of a “stability balance,” roughly illustrated by Figs 16

and 17, in conjunction with either an outside or inside model of

the vessel, the moments of stability can be practically determined.

In practice, an inside model has been found the most convenient to

employ. This consists of a number of rectangular pieces of yellow

pine of any uniform thickness, out of which a portion has been cut,

respectively to the form of the vessel at equidistant intervals of

say 15 feet. These pieces, together with two end pieces, are kept

together by four or six bolts, thus forming a contracted model, the

inside of which is of a similar form to that of the vessel. If

this model is filled with water to a height corresponding to any

draught, it will represent a volume of water having the same form,

and proportional to the displacement of the vessel at that draught.

The stability balance consists of a frame =A= attached to a steel

bar =Z=, having knife edges working upon the support =C=; a table

=D= attached to a spindle working freely in the bearings =E=, and

capable of being turned through any angle; a sliding weight =F= to

balance the weight of the model when empty; a sliding weight =H=

to balance and measure the weight of the water contained in inside

or displaced by outside models; a sliding balance weight =K= which

by adjustment will locate the centre of gravity of the combined

weights of the table =D=, the model and the weight =K= in the axis

of the table =D=, so that the model will remain when empty in any

inclined position, and be balanced by the weight =F=.

In order to determine the moments of stability, the model is first

fixed on the table =D=, and the weights =F= and =K= so adjusted

that =F= will balance the model at all inclinations. The table is

then brought into the upright position, and water is poured into

the model to the height corresponding to the desired draught of

water, and the weight =H= shifted until the whole is balanced.

The weight of water in the model will evidently be = weight =H= ×

its distance from the fulcrum ÷ distance centre of model is from

fulcrum.

If the table with the model is now turned through any angle, the

distance the centre of gravity of the water has moved from the axis

=E= of the table can easily be determined by shifting the weight

=H= until the whole is balanced, then evidently from the principles

of the lever, =H= × by its distance from fulcrum = weight of water

in model × by the distance the centre of gravity of the water in

the model is from fulcrum. Since the weight of =H= × its distance

from fulcrum ÷ the weight of water in model is known, the distance

that the centre of gravity of the water has shifted from centre

line is easily ascertained and the righting lever determined.

From a lengthened series of experiments, conducted by Mr

Heck—latterly in Messrs Denny’s Works where an apparatus from a

special design by Mr Heck has been constructed for the firm’s use—the

method gives promise of taking a firm place as an extremely simple

and approximately accurate means of arriving at the stability of

vessels.[18]

While a vessel’s qualities with respect to stability may be

determined with great precision by the naval architect, his

investigations are only directly applicable to the ship while empty

or when in certain assumed conditions of loading which may or may

not often occur in actual service. He cannot for obvious reasons

estimate, far less control, the amounts and positions of centre

of gravity of the various items of weight that may make up the

loading.[19] This aspect of the subject has received attention at the

hands of naval architects for a considerable time, but the forcible

way in which it has been brought under view by recent experience

has resulted in special efforts being made to practically meet the

necessities of the case. In 1877 Mr William John read a paper before

the Institution of Naval Architects, in which he dealt with the

effect of stowage on the stability of vessels, and since that time

such authorities as Martell, White, and Denny have given valuable

papers or made suggestive comments bearing on this important matter.

Much has also been done by several builders in the way of devising

diagrams useful for regulating stowage and manipulating ballast with

regard to initial stability. At the last meeting of the Institution,

Professor Elgar read a paper on “The Use of Stability Calculations

in Regulating the Loading of Steamers,” distinguished by its

eminently practical character, and forming an important contribution

to the solution of this problem. The author disapproved of curves

of stability being supplied with vessels, as had been advised and

was then becoming the practice. General notes, giving in a simple

form easily applied in daily practice, particulars respecting the

character of a ship’s stability in different conditions, are what

the author recommended and had found through actual experience to

meet the case most effectually. In the discussion which followed

it was intimated by Mr William Denny that his firm had already

resolved to furnish every new steamer produced by them with a volume

containing general and special notes and diagrams dealing not only

with stability but with several other important technical properties

(see footnote, page 59). After consultation with Professor Elgar,

however, he had abandoned his intention of supplying stability curves.

An arrangement designed to readily find the position of the centre

of gravity experimentally by inclining, and to indicate at once the

stability of loaded vessels as represented by metacentric height, has

been devised and introduced on board several ships by Mr Alexander

Taylor, of Newcastle—already referred to in connection with the

triple expansion principle in marine engines. The instrument and

apparatus, which he appropriately names the “Stability Indicator,”

was described in a paper read by him before the Institution of Naval

Architects at its last meeting. When once an inclining operation

has been made, the degree of inclination is read from a glass gauge

and the position of centre of gravity and corresponding metacentric

height from a previously prepared scale set up alongside the gauge,

or from tabulated figures.

* * * * *

The advance made within recent years in connection with steam

propulsion comprises many matters necessarily left unconsidered in

the chapter on speed and power of modern steamships. Scientific

methods have undoubtedly contributed in no small degree to the

realization of the remarkable results therein outlined. The

achievement of one triumph after another as demonstrated in the

actual performances of new vessels, and especially the confidence

with which pledges of certain results are given and received long

before actual trials are entered upon—and that sometimes with regard

to ships embodying very novel features—are evidences of the truth of

this.

The oldest method of approximating to the horse-power required

to propel a proposed vessel at a given speed is to compare the

new ship with ships already built by the use of formulæ known

as “co-efficients of performance” deduced from the results of

their speed trials. Two such co-efficients have been deduced from

Admiralty practice, the one involving displacement, the other area of

mid-section, with speed as the variable in both cases. Another method

which has been largely used, consists in first determining the ratio

of the indicated horse-power to the amount of “wetted surface,” or

immersed portion of the vessel’s skin, in the exemplar ship, and then

estimating from this ratio the probable value of the corresponding

ratio for the proposed ship at her assigned speed. Inasmuch as these

methods of procedure do not take account of the _forms_ of the hulls,

and consequently of that factor in the total resistance due to

_wave-making_, they cannot be used with any degree of confidence, or

without large corrections, except in connection with vessels whose

speeds are moderate in proportion to their dimensions: those in fact

in which the resistance varies nearly as the square of the speed. A

further method, somewhat resembling the one based upon the relation

between indicated horse-power and the “wetted surface,” was proposed

by the late Prof. Rankine, but has never been extensively employed.

Apart from the unreliable nature of the results which an application

of it gives—except for certain speeds—it is open to several serious

objections in practice.

A method of analysis and prediction, meeting with considerable

acceptance from shipbuilders on the Clyde and elsewhere, has been

introduced within recent years by Mr A. C. Kirk, of Messrs R. Napier

& Sons.[20] The method consists in reducing all vessels to a definite

and simple form, such as readily admits of comparison being made

between their immersed surface, length of entrance and angle of

entrance and their indicated horse-power, and from this judging of

the form and proportions best suited to a given speed or power in

proposed vessels. The form in question consists of a block model,

having a rectangular midship section, parallel middle body, and

wedge-shaped ends; its length being proportioned to that of the ship,

its depth to the mean draught of water, its girth of mid-section

to the girth of immersed mid-section of the ship, and the surface

of its sides, bottom and ends, to the immersed surface of the ship.

By finding from one or more exemplar ships—the selection of which

is obviously governed by the conditions of analysis—the rate of

indicated horse-power required per unit of wetted surface at the

speed assigned for the proposed vessel, the appropriate rate for the

latter may easily be determined.

The data afforded by the modern system of progressive speed trials,

especially when taken in conjunction with that of experiment with

models as systematised by Mr Froude, supplies in a reliable way

much of what is most lacking in the older methods of comparison and

prediction. Progressive speed trials on the measured mile were first

systematically instituted by Mr William Denny about nine years ago,

since which it has been the practice of his firm to make such trials

with all their vessels. The practice has been followed by other firms

on the Clyde and elsewhere, and there is every probability it will

be still more widely adopted in the future. The system consists in

trying the vessel at various speeds, ranging from the highest to

about the lowest of which she is capable. The several speeds are the

mean of two runs—one run with the tide and one against, the object

being to eliminate the tide’s influence from the results.[21]

Essentially noteworthy in connection with the system is the manner

in which the data obtained from the trials is recorded for future

use. This consists of a series of curves, representing the chief

properties of ship, engines, and propeller—_e.g._, “speed and power,”

“revolutions” and “slip”—which show to the eye, more easily and

clearly than bare figures, the whole course and value of a steamer’s

performances. For that of speed and power the various speeds made at

the trials are set off to convenient scale as horizontal distances,

and the indicated horse-power corresponding to those speeds are set

off to scale as vertical distances. The intersection of the offsets

so made, give spots for the curve. The other curves alluded to are

similarly constructed, the requisite data being the direct or deduced

results of the measured mile trials.

From the accumulation of trial results thus graphically recorded

the designer of new ships can proceed to estimate with greater

assurance of attaining satisfactory results than by employing the

older methods. If, for example, a ship is to be built of virtually

similar dimensions and form to one for which such information is

available, but of less speed, the task is simply one of measurement

from the curves, with some allowance for probable differences in

the constant friction of the engines. If the speed is to be greater

than that of the exemplar ship, but still within the limits when

wave-making resistance assumes relative importance, the case is also

one of simple reading from the curves, with slight corrections.

When both the speed and size are different, but the form is

approximately the same, the case is more difficult, but it can be

dealt with approximately by employing the “law of comparison” or of

“corresponding speeds” enunciated by Mr Froude. Formulæ based upon

this law—which will be more fully referred to presently—have been

devised by one or two designers, and applied by them to problems of

the latter class as they occurred in the course of their professional

work. Mr John Inglis, junr., described a method of analysis he had

adopted, involving the use of Mr Froude’s law, in a paper read before

the Institution of Naval Architects in 1877.

When unusual speeds are aimed at, or when novel types of vessels have

to be dealt with, the only available method of making a trustworthy

estimate of the power required lies in the use of direct or

deduced results from model experiments. Mr Froude began the work

of speed experiments with ships’ models on behalf of the Admiralty

at the Experimental Tank in Torquay about 1872, carrying it on

uninterruptedly until his death in May, 1879. Since that lamented

event the work has been continued with most gratifying results by his

son, Mr R. E. Froude. Experiments had, of course, been made by many

other investigators previous to Mr Froude, but none before or since

have made model experiments so practically useful and reliable. Since

the value of the work carried on at Torquay has become appreciated,

several experimental establishments of a similar character have been

instituted. The Dutch Government, in 1874, formed one at Amsterdam,

which, up till his death in 1883, was under the superintendence of

Dr Tideman, whose labours in this direction were second only to

those of the late Mr Froude. It is now superintended by Mr A. J. H.

Beeloo, Chief Constructor, and under him by Mr H. Cop. It was here,

it may be remembered, that experiments were made with a model of the

Czar of Russia’s yacht _Livadia_, previous to the construction of

that extraordinary vessel being begun by Messrs Elder & Co. On the

strength of the data so obtained, together with the results of the

trials made on Loch Lomond with a miniature of the actual vessel,

those responsible for her stipulated speed were satisfied that it

could be attained. The actual results as to the speed of the novel

vessel amply justified the reliance put upon such experiments. In

1877 the French naval authorities established an experimental tank

in the dockyard at Brest, and the Italian Government have formed

one in the naval dockyard at Castellamare. The only experimental

tank hitherto established by a private mercantile firm is that in

the shipyard of Messrs Denny, Dumbarton. This establishment is on a

scale of completeness not surpassed elsewhere, and is fitted with

every appliance which the latest experience in such experiments shows

to be advantageous. A special staff of experimentalists, forming

a branch of the general scientific body, are engaged conducting

experiments and accumulating data, which, besides being of service in

their present daily practice, must ultimately yield fruit of a very

special kind to this enterprising firm.[22]

From mathematical reasoning, and by means of an extended series of

experiments with models and actual ships, Mr Froude determined that

for two vessels of similar form—for instance a ship and her model—the

“corresponding speeds” of ship and model are to one another as the

square roots of the similar dimensions, and at corresponding speeds

the resistance of ship and of model are to one another as the cubes

of the similar dimensions—subject to a correction concerned with skin

friction necessitated by the difference in the lengths of ship and

model.[23] Having obtained the resistance of a model, and from it,

by an application of the above law, deduced the resistance of the

full-sized vessel, the effective horse-power is found by multiplying

the resistance by the speed of the vessel in feet per minute, and

dividing by 33,000. From the effective horse-power an estimate of the

indicated horse-power required can be made by using ratios which the

one bore to the other in former ships, as obtained from a comparison

of their model experiments with their measured mile trial results.

The value of progressive speed trials and of experiments with models

as affording convenient means whereby analysis may be made of the

several sources of expenditure of power in propelling vessels can

scarcely be over-estimated.

From a study of the graphic records of progressive trials, and from

model experiment results, Mr Froude discovered a method whereby the

power expended in overcoming the frictional resistance of the engines

could be determined, and estimates made of the amount of power

absorbed by other elements. The method in question was communicated

in full in a paper read before the Institution of Naval Architects

in 1876, and has since been extensively used. Methods of analysis

resulting from a simultaneous study of this subject, were also

proposed by Mr Robert Mansel, a prominent Clyde shipbuilder and noted

investigator, but they failed in meeting with the acceptance which

was at once accorded to Mr Froude’s propositions.[24]

Although the results obtained by an application of Mr Froude’s

analysis to the trials of a large number of merchant vessels have

undoubtedly thrown considerable light on the relative efficiency of

hull and engines, and of various types of engines, still, for several

reasons adduced by extended experience—most of which, indeed, were

foreseen and perfectly appreciated by Mr Froude himself—the need has

been felt for some means of directly measuring the power actually

delivered to the propellers by the engines when working at different

speeds. One of Mr Froude’s latest inventions, the perfecting of

which was not accomplished until after his death, consisted of a

dynamometric apparatus designed to accomplish this important end.[25]

The construction of the instrument was undertaken for the Admiralty,

and trials were made with it on H.M.S. _Conquest_ in the early part

of 1880. The results of these experiments have not yet in any form

been recorded, but there can be no question as to the benefit that

would accrue to the profession if the Admiralty could be induced to

publish these, as well as the results of other experiments with this

instrument.