————————————————————————————————————————————————————————————_The Steam Engine Explained and Illustrated (Seventh Edition) With an Account of Its Invention and Progressive Improvement, and Its Application to Navigation and Railways; Including Also a Memoir of Watt

Names. | of | of | | of | of

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| Ft. | Ft. | Ft. | Ft. | Ft.

Providence | 180 | 27 | 9 | —— | ——

Lexington | 207 | 21 | —— | 23 | 9

Narragansett | 210 | 26 | 5 | 25 | 11

Massachusetts | 200 | 29·5 | 8·5 | 22 | 10

Rhode Island | 210 | 26 | 6·5 | 24 | 11

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Names. | of | of | of | of | of | Stroke

| In. | | In. | Ft. | |

Providence | —— | 1 | 10 | 65 | |

Lexington | 30 | 1 | 11 | 48 | 24 |

Narragansett | 30 | 1 | 60 | 12 | 2 | 1/2

Massachusetts | 28 | 2 | 44 | 8 | 26 |

Rhode Island | 30 | 1 | 11 | 60 | 21 |

The Narragansett, the finest of these vessels, is built of oak,

strengthened by diagonal straps or ties of iron, by which her

timbers are connected; she is driven by a condensing engine, and

has two boilers, exposing about three thousand square feet of

surface to the fire. The steam is maintained at a pressure of from

twenty to twenty-five lbs. per square inch: the cylinder is

horizontal.

The cabins of these sea-boats are of great magnitude, and afford

excellent accommodation for passengers, containing generally four

hundred berths. In the Massachusetts the chief cabin is one hundred

and sixty feet long, twenty-two feet wide, and twelve feet in

height, its vast extent being uninterrupted by pillars or any other

obstruction. "I have dined," says Mr. Stevenson, "with one hundred

and seventy-five persons in this cabin, and, notwithstanding this

numerous assembly, the tables, which were arranged in two parallel

rows, extending from one end of the cabin to the other, were far

from being fully occupied, the attendance was good, and every thing

was conducted with perfect regularity and order. There are one

hundred and twelve fixed berths ranged round this cabin, and one

hundred temporary berths can be erected in the middle of the floor:

besides these there are sixty fixed berths in the ladies' cabin, and

several temporary sleeping [Pg498] places can be erected in it

also. The cabin of the Massachusetts is by no means the largest in

the United States. Some steamers have cabins upwards of one hundred

and seventy-five feet in length. Those large saloons are lighted by

Argand lamps, suspended from the ceiling, and their appearance, when

brilliantly lighted up and filled with company, is very remarkable.

The passengers generally arrange themselves in parties at the

numerous small tables into which the large tables are converted

after dinner, and engage in different amusements. The scene

resembles much more the coffee-room of some great hotel than the

cabin of a floating vessel."

(234.) Nothing has excited more surprise among engineers and

others interested in steam navigation in Europe, than the

statements which have been so generally and so confidently made of

the speed attained by American steamers. This astonishment is due

to several causes, the chief of which is the omission of all

notice of the great difference between the structure and operation

of the American steamers and the nature of the navigation in which

they are engaged, compared with the structure and operation of,

and the navigation in which European steamers are employed: as

well might the performance of a Thames wherry, or one of the

fly-boats on the northern canals, be compared with that of the

Great Western, or the British Queen. The statements alluded to all

have reference to steamers navigating the Hudson between New York

and Albany, the form and structure of which we have already

described; and doubtless the greatest speed ever attained on the

surface of water has been exhibited in the passages of these

vessels.

Mr. Stevenson states, that exclusive of the time lost in

stoppages, the voyage between New York and Albany is usually made

in ten hours. Dr. Renwick, however, who has probably more

extensive opportunities of observation, states, that the average

time, exclusive of stoppages, is ten hours and a half. The

distance being 125·18 geographical miles, the average rate would

therefore be 11-9/10 miles per hour. If it be observed that the

average rate of some of the best sea-going steamers in Europe

obtained from experiments [Pg499] and observations made by

myself, more than three years ago, showed a rate of steaming

little less than ten geographical miles per hour, and that since

that time considerable improvements in steam navigation have been

made, and further, that these performances were made under

exposure to all the disadvantages of an open sea, the difference

between them and the performance of the American river steamers

will cease to create astonishment.

Dr. Renwick states that he made, in a boat called the "New

Philadelphia," one of the most remarkable passages ever performed.

He left New York at five in the afternoon, with the first of the

flood, and landed at Catskill, distant 95·8 geographical miles

from New York, at a quarter before twelve. Passengers were landed

and taken in at seven intermediate points: the rate, including

stoppages, was therefore 14·2 miles per hour; and if half an hour

be allowed for stoppages, the actual average rate of motion would

be fifteen miles and three quarters an hour. As the current, which

in this case was with the course of the vessel, did not exceed

three miles and a half an hour, the absolute velocity through the

water would have been somewhat under twelve miles an hour. This

speed is nearly the same as the speed obtained from taking the

average time of the voyages between New York and Albany at ten

hours and a half; it would therefore appear that the great speed

attained in this trip must have been chiefly, if not altogether,

owing to the effect of the current.

(235.) The steamers which navigate the great northern lakes differ

so little in their construction and appearance from the European

steam-boats, that it will not be necessary here to devote any

considerable space to an account of them. These vessels were

introduced on the lakes at about the same time that steamers were

first introduced on the Clyde. These steamers are strongly built

vessels, supplied with sails and rigging, and propelled by

powerful engines. The largest in 1837, when Mr. Stevenson visited

the States, was the _James Madison_. This vessel was one hundred

and eighty-one feet in length on the deck, thirty feet in breadth

of beam, and twelve feet six inches in depth of hold: her draught

of water was ten feet, and her measured capacity seven hundred

[Pg500] tons. She plyed between Buffalo on Lake Erie and Chicago

on Lake Michigan, a distance of nine hundred and fifty miles.

The severe storms and formidable sea encountered on the lakes

render necessary for the navigation, vessels in all respects as

strong and powerful as those which navigate the open ocean.

(236.) By far the most remarkable and important of all the

American rivers is the Mississippi and its tributaries. That part

of the American continent which extends from the southern shores

of the great northern lakes to the northern shores of the Gulf of

Mexico, is watered by these great streams. The main stream of the

Mississippi has its fountains in the tract of country lying north

of the Illinois and east of Lake Michigan, in latitude forty-three

degrees. At about latitude thirty-nine degrees, a little north of

St. Louis, it receives the waters of the Missouri, and further

south, at the latitude of thirty-seven degrees, the Ohio flows

into it, after traversing five degrees of longitude and four of

latitude, and winding its way from the Alleghany range through

several of the states, and forming a navigable communication with

numerous important towns of the Union, among which may be

mentioned Pittsburg, Cincinnati, Frankfort, Lexington, and

Louisville. The main stream of the Mississippi, after receiving

the waters of the Arkansas, and numerous other minor tributaries,

flows into the Gulf of Mexico by four mouths. The main stream of

the Mississippi, independently of its tributaries, forms an

unbroken course of inland navigation for a distance of nearly two

thousand three hundred miles. Its width, through a distance of one

thousand one hundred miles from its mouth, is not less than half a

mile, and its average depth a hundred feet. The Ohio, its chief

eastern tributary, flowing into it at a distance of about a

thousand miles from its mouth, traverses also about the same

extent of country, and is navigable throughout the whole of that

extent. This river also has several navigable tributaries of

considerable extent, among which may be mentioned the Muskingum,

navigable for one hundred and twenty miles; the Miami, navigable

for seventy-five miles; the Scioto, navigable for one hundred and

twenty [Pg501] miles; the Tennessee, navigable for two hundred

and fifty miles; the Cumberland, navigable for four hundred and

forty miles; the Kentucky, navigable for one hundred and thirty

miles; and the Green River, navigable for one hundred and fifty

miles. The total length of the Ohio and its tributaries is

estimated at above seven thousand miles.

(237.) Steam-boats were introduced on the Mississippi about the

year 1812, the period of their first introduction in Europe; and

their increase has been rapid beyond all precedent. In the year

1831 there were one hundred and ninety-eight steamers plying on

its waters; and the number in 1837 amounted to nearly four

hundred. These vessels are built chiefly on the banks of the Ohio,

at the towns of Pittsburg and Cincinnati, at distances of about

two thousand miles from the mouth of the river they are intended

to navigate.

(238.) These steamers, which are decidedly inferior to those which

navigate the eastern waters, are generally of a heavy build,

fitted to carry goods as well as passengers, and vary from one

hundred to seven hundred tons burthen. Their draught of water is

also greater than that of the eastern river steamers—varying from

six to eight feet. The hull, at about five feet from the water

line, is covered with a deck, under which is the hold, in which

the heavy part of the cargo is stowed. About the middle of this

deck the engines are placed, the boilers and furnaces occupying a

space nearer to the bow, near which two chimneys are placed. The

fire-doors of the furnaces are presented towards the bow, and

exposed so as to increase the draught. That part of the first deck

which extends from the machinery to the stern is the place

allotted to the crew and the deck passengers, and is described as

being filthy and inconvenient in the extreme. A second deck is

constructed, which extends from the chimneys near the bow to the

stern of the vessel. On this is formed the great cabin or saloon,

which extends from the chimneys to within about thirty feet of the

stern, where it is divided by a partition from the ladies' cabin,

which occupies the remaining space. These principal cabins are

surrounded by a gallery about three feet in width, from which, at

convenient [Pg502] places, an ascent is supplied by stairs to the

highest deck, called the hurricane or promenade deck.

(239.) The engines by which these boats are propelled are totally

different from the machinery already described as used in the

eastern steamers. They are invariably non-condensing engines,

worked by steam of extremely high pressure; the boilers are

therefore tubular, and the cylinders small in diameter, but

generally having a long stroke.

The pressure of steam used in these machines is such as is never

used in European engines, even when worked on railways. A pressure

of one hundred pounds per inch is here considered extremely

moderate. The captain of one of these boats, plying between

Pittsburg and St. Louis, told Mr. Stevenson that "under ordinary

circumstances his safety valves were loaded with a pressure equal

to one hundred and thirty-eight pounds per square inch, but that

the steam was occasionally raised as high as one hundred and fifty

pounds to enable the vessel to pass parts of the river in which

there is a strong current;" and he added, by way of consolation,

that "this pressure was never exceeded except on _extraordinary

occasions_!"

The dimensions and power of the Mississippi steamers may be

collected from those of the St. Louis, a boat which was plying on

that river in 1837. That vessel measured two hundred and fifty

feet on deck, and had twenty-eight feet breadth of beam. Her

draught of water was eight feet, and her measured capacity one

thousand tons. She was propelled by two engines with thirty-inch

cylinders, and ten feet stroke; the safety valve being loaded at

one hundred pounds per square inch.

The paddle wheels of these vessels are attached to the paddle

shaft, in such a manner as to be thrown into and out of gear, at

discretion, by the engineer, so that the paddle shaft may revolve

without driving the wheels: by this expedient the power of the

engine is used to feed the boilers while the vessel stops at the

several stations. The vessel is therefore stopped, not, as is

usually the case, by stopping the engines, but by throwing the

wheels out of connection with the paddle shaft. The engines

continue to work, but their [Pg503] power is expended in forcing

water into the boiler. By this expedient the activity of the

engines may, within practical limits, be varied with the

resistance the vessel has to encounter. In working against a

strong current, the feed may be cut off from the boilers, and the

production of steam, and consequently the power of the engines,

thereby stimulated, while this suspension of the feed may be

compensated at the next station.

The stoppages to take in goods and passengers, and for relays of

fuel, are frequent. "The liberty which they take with their

vessels on these occasions," says Mr. Stevenson, "is somewhat

amusing: I had a good example of this on board a large vessel,

called the Ontario. She was steered close in shore amongst stones

and stumps of trees, where she lay for some hours to take in

goods: the additional weight increased her draught of water, and

caused her to heel a good deal; and when her engines were put in

motion, she actually _crawled_ into the deep water on her paddle

wheels: the steam had been got up to an enormous pressure to

enable her to get off, and the volume of steam discharged from the

escapement pipe at every half stroke of the piston made a sharp

sound almost like the discharge of fire-arms, while every timber

in the vessel seemed to tremble, and the whole structure actually

groaned under the shocks."

Besides the steamers used for the navigation of the Mississippi,

innumerable steam tugs are constantly employed in towing vessels

between the port of New Orleans and the open sea of the Gulf of

Mexico. Before the invention of steam navigation, this southern

capital of the United States laboured under the disadvantage of

possessing almost the only bad and inconvenient harbour in the

vast range of coast by which the country is bounded. New Orleans

lies at a distance of about one hundred miles from the Gulf of

Mexico. The force of the stream, the frequency of shoals, and the

winding course of the channel rendered it scarcely possible for a

sailing vessel to pass between the port and the sea with the same

wind. The anchorage was every where bad, and great difficulty and

risk attended the mooring of large vessels to the banks. The steam

engine has, however, overcome all [Pg504] these difficulties, and

rendered the most objectionable harbour of the Union a safe and

good seaport, perfectly easy of approach and of egress at all

times; a small steam tug will take in tow several large ships, and

carry them with safety and expedition to the offing, where it will

dismiss them on their voyage, and take back vessels which may have

arrived.

[Illustration: GREAT WESTERN OFF NEW YORK.]

[Pg505]

APPENDIX.

_On the Relation between the Temperature, Pressure, and Density_

_of Common Steam._

There is a fixed relation between the temperature and pressure of

common steam, which has not yet been ascertained by theory.

Various empirical formulæ have been proposed to express it,

derived from tables of temperatures and corresponding pressures

which have been founded on experiments and completed by

interpolation.

The following formula, proposed by M. Biot, represents with great

accuracy the relation between the temperature and pressure of

common steam, throughout all that part of the thermometric scale

to which experiments have been extended.

Let

a = 5·96131330259

log. a_{1} = 0·82340688193 − 1

log. b_{1} = −·01309734295

log. a_{2} = 0·74110951837

log. b_{2} = −·00212510583

The relation between the temperature t with reference to the

centesimal thermometer, and the pressure p in millimètres of

mercury at the temperature of melting ice, will then be expressed

by the following formula:—

log. p = a − a_{1}b_{1}^{20 + t} − a_{2}b_{2}^{20 + t}. (1.)

Formulæ have, however, been proposed, which, though not applicable

to the whole scale of temperatures, are more manageable in their

practical application than the preceding.

For pressures less than an atmosphere, Southern proposed the

following formula, where the pressure is intended to be expressed

[Pg506] in pounds per square inch, and the temperature in

reference to Fahrenheit's thermometer,—

p = 0·04948 + ((51·3 + t) / 155·7256)^{5·13} |

|. (2.)

t = 155·7256 ((p − 0·04948) − 51·3)^{1/(5·13)} |

The following formula was proposed by Tredgold, where p expresses

the pressure in inches of mercury:—

p = ((100 + t) / 177)^{6}.

This was afterwards modified by Mellet, and represents with

sufficient accuracy experiments from 1 to 4 atmospheres. Let p

represent pounds per square inch, and t the temperature by

Fahrenheit's thermometer,—

p = ((103 + t) / 201·18)^{6} |

|. (3.)

t = 201·18 p^{1/6} − 103 |

M. de Pambour has proposed the following formula, also applicable

through the same limits of the scale:—

p = ((98·806 + t) / 198·562)^{6} |

|. (4.)

t = 198·562 p^{1/6} − 98·806 |

MM. Dulong and Arago have proposed the following formula for all

pressures between 4 and 50 atmospheres:—

p = (0·26793 + 0·0067585 t)^{5} |

|. (5.)

t = 147·961 p^{1/5} − 39·644 |

It was about the year 1801, that Dalton, at Manchester, and

Gay-Lussac, at Paris, instituted a series of experiments on

gaseous bodies, which conducted them to the discovery of the law

mentioned in art. (96.), p. 171. These philosophers found that all

gases whatever, and all vapours raised from liquids by heat, as

well as all mixtures of gases and vapours, are subject to the

_same quantity of expansion_ between the temperatures of melting

ice and boiling water; and by experiments subsequently made by

Dulong and Petit, this uniformity of expansion has been proved to

extend to all temperatures which can come under practical

inquiries.

Dalton found that 1000 cubic inches of air at the temperature of

melting ice dilated to 1325 cubic inches if raised to the

temperature of boiling water. According to Gay-Lussac, the

increased volume was 1375 cubic inches. The latter determination

has been subsequently found to be the more correct one.[40]

[Pg507] It appears, therefore, that for an increase of temperature

from 32° to 212°, amounting to 180°, the increase of volume is 375

parts in 1000; and since the expansion is uniform, the increase of

volume for 1° will be found by dividing this by 180, which will

give an increase of 208-1/3 parts in 100,000 for each degree of

the common thermometer.

To reduce the expression of this important and general law to

mathematical language, let v be the volume of an elastic fluid at

the temperature of melting ice, and let nv be the increase which

that volume would receive by being raised one degree of

temperature under the same pressure. Let V be its volume at the

temperature T. Then we shall have

V = v + nv (T − 32) = v (1 + n (T − 32)).

If V′ be its volume at any other temperature T′, and under the

same pressure, we shall have, in like manner,

V′ = v (1 + n (T′ − 32)).

Hence we obtain

V/V′ = (1 + n (T − 32)) / (1 + n (T′ − 32)); (6.)

which expresses the relation between the volumes of the same gas

or vapour under the same pressure and at any two temperatures. The

co-efficient n, as explained in the text, has the same value for

the same gas or vapour throughout the whole thermometric scale.

But it is still more remarkable that this constant has the same

value for all gases and vapours. It is a number, therefore, which

must have some essential relation to the gaseous or elastic state

of fluid matter, independent of the peculiar qualities of any

particular gas or vapour.

The value of n, according to the experiments of Gay-Lussac, is

0·002083, or 1/480.

To reduce the law of Mariotte, explained in (97.) p. 171., to

mathematical language, let V, V′ be the volumes of the same gas or

vapour under different pressures P, P′, but at the same

temperature. We shall then have

VP = V′P′. (7.)

If it be required to determine the relation between the volumes of

the same gas or vapour, under a change of both temperature and

pressure, let V be the volume at the temperature T and under the

pressure P, and let V′ be the volume at the temperature T′ and

under the pressure P′. Let v be the volume at the temperature T

and under the pressure P′.

By formula (7.) we have

VP = vP′;

[Pg508] and by formula (6.) we have

(V′/v) = (1 + n(T′ − 32)) / (1 + n(T − 32))

Eliminating v, we shall obtain

(V/V′) = (P′/P) · (1 + n(T − 32)) / (1 + n(T′ − 32));

or,

(VP/V′P′) = (1 + n(T − 32)) / (1 + n(T′ − 32)); (8.)

which is the general relation between the volumes, pressures, and

temperatures of the same gas or vapour in two different states.

To apply this general formula to the case of the vapour of water,

let T′ = 212°. It is known by experiment that the corresponding

value of P′, expressed in pounds per square inch, is 14·706; and

that V′, expressed in cubic inches, the water evaporated being

taken as a cubic inch, is 1700. If, then, we take 0·002083 as the

value of n, we shall have by (8.),

VP = 1700 × 14·706 × (1 + 0·002083 (T − 32)) / (1 + 0·002083 × 180)

= 18183(1 + 0·002083 (T − 32)). (9.)

If, by means of this formula (9.), and any of the formulæ (1.),

(2.), (3.), (4.), (5.), T were eliminated, we should obtain a

formula between V and P, which would enable us to compute the

enlargement of volume which water undergoes in passing into steam

under any proposed pressure. But such a formula would not be

suitable for practical computations. By the formulæ (1.) to (5.),

a table of pressures and corresponding temperatures may be

computed; and these being known, the formula (9.) will be

sufficient for the computation of the corresponding values of V,

or the enlargement of volume which water undergoes in passing into

steam.

In the following table, the temperatures corresponding to

pressures from 1 to 240 lbs. per square inch are given by

computation from the formulæ (2.) to (5.), and the volumes of

steam produced by an unit of volume of water as computed from the

formula (9.).

The mechanical effect is obtained by multiplying the pressure in

pounds by the expansion of a cubic inch of water in passing into

steam expressed in feet, and is therefore the number of pounds

which would be raised one foot by the evaporation of a cubic inch

of water under the given pressure. [Pg509]

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