knowing a letter, or interweaving any thing suspicious of other
secret than a new-fashioned riband.
NOTE.
The evident analogy between this Article and No. XXXIII. will
be apparent on the slightest view, and in general principle it
is similar to Nos. XXXIV. XXXV., &c. It may be performed either
by making the stitches of a given length, varying the distance
to distinguish the different letters of the alphabet; or, by
any arbitrary shape which may be previously agreed upon by the
parties corresponding. These arrangements being made, the silk
weaver will have nothing more to do, than set his loom to the
required pattern.
No. LXXVI.
How to write in the dark, as straight as by day or candle-light.
NOTE.
Two planes of ebony of equal length and breadth, similar to the
parallel ruler, and joined at each end by racks, the side of
which being graduated to the width of the line intended will
serve as a certain guide, and by the use of this instrument a
blind person may write with the greatest accuracy. If ivory
tablets or a slate is used, a fine wire drawn with a steel point
may be readily felt by the point of the pencil.
No. LXXVII.
How to make a man to fly: which I have tried with a little boy of
ten years old, in a barn, from one end to the other, on a hay-mow.
NOTE.
Innumerable are the schemes that have been proposed by the
learned at different periods, to enable man to support himself
in the air by the means of artificial wings, &c. and some,
indeed, of these ingenious contrivances have formed the labours
of the most distinguished mechanical geniuses, which are
recorded in the early annals of science.
Bacon, and an Italian priest named Francisco Lana, endeavoured
to accomplish it by means of two thin hollow globes, exhausted
of air, which being considerably lighter than that fluid, were
intended to sustain a chair suspended to their lower extremity,
and on which the aeronaut might be seated. But Dr. Hook, in a
work published some time after the _Prodromo_ of Lana, plainly
showed the fallacy of the attempt, though without in the least
attempting to deny the possibility of eventually effecting this
object.
Bishop Wilkins, who was also a disciple of the flying system,
describes a species of land-sailing vessels or chariots, which
were then commonly used in China: and it is rather a curious
fact that a German Count, possessing as much of modesty as the
generality of foreign mechanics, has lately given to the public,
as his own, an invention which has been known in Europe, and
occasionally employed in Asia, for the last four hundred years.
But of all the plans that have hitherto been devised, those only
which have mechanic power as their basis appear to have any
chance of success. This may be considered as an unerring _datum_
to guide the future experimentalist, the certainty of which
is fully demonstrated by a comparison of the powers of the
human frame with those of the feathered tribe: for it has been
calculated by an ingenious anatomist, that the muscles which
move the wings downwards in a bird in many instances, constitute
not less than the sixth part of the weight of the whole body;
while those of a man are not one hundredth part so large. By the
use of springs, however, wound to a certain degree of tension,
prior to embarking upon the intended expedition, and acting
upon cranks working the wings, the same power as that possessed
by the feathered race may be obtained, and the springs may be
readily made to draw more than fifty times their weight. By
this means a whalebone, or other light carriage, may be raised,
though it would be but for a short time, as it would not be in
the power of the aëronaut to wind the springs so quick as the
machine would require.
From this, then, it will be seen that, to produce the effect
necessary for this species of navigation, it is only requisite
to have a first mover, which will produce more power, in a given
time, in proportion to its weight, than the animal system of
muscles.
High pressure steam-engines have been made to operate by
expansion only, and they, it appears, might be constructed so
as to be light enough for this purpose. In that case, however,
it will be evident that the usual plan of a large boiler must
be given up, and the principle of injecting a proper charge of
water into a series of tubes, forming the cavity of the fire,
must be adopted in lieu of it.
The following estimate will show the probable weight of such an
engine with its charge for one hour.
lbs.
The engine itself, from 90 to 100
Weight of inflamed coals in a }
cavity presenting about 4 feet } 25
surface of tube }
Supply of coal for 1 hour 6
Water for ditto, allowing steam }
of one atmosphere to be 1/1800 } 32
the specific gravity of water }
---
163
---
It may at first view appear superfluous to inquire further
relative to a first mover for aërial navigation; but lightness
is of so much value in this instance, that it is proper to
notice the probability that exists of using the expansion of air
by the sudden combustion of inflammable powders or fluids with
great advantage. The French have experimentally shown the great
power produced by igniting inflammable fluids in close vessels;
and several years ago, an engine was made in this country to
work in a similar manner, by the inflammation of spirit of tar.
It appears that eighty drops of this fluid raised eight hundred
weight to the height of 22 inches; hence a one-horse power may
consume from 10 to 12 pounds per hour, and the engine itself
need not exceed 50 pounds weight.
Probably a much cheaper engine of this sort might be produced
by gas-light apparatus, and by firing the inflammable air
generated, with a due portion of common air, under a piston.
Upon some of these principles it is perfectly clear that force
can be obtained by a much lighter apparatus than the muscles of
animals or birds, and therefore in such proportion may aërial
vehicles be loaded with inactive matter. Even the high pressure
steam-engine doing the work of six men, and only weighing
equal to one, will readily raise five men into the air, but by
increasing the magnitude of the engine ten, fifty; or even five
hundred men may equally well be conveyed.
Having rendered the accomplishment of this object probable upon
the general view of the subject, it will now be necessary to
point out the principles of the art itself. The whole problem
is confined within these limits, viz. To make a surface support
a given weight by the application of power to the resistance of
the surrounding atmosphere.
Many experiments have been made upon the direct resistance of
air by Mr. Robins, Mr. Rouse, Mr. Edgeworth, Mr. Smeaton, and
others. The result of Mr. Smeaton's experiments and observations
was, that a surface of one square foot met with a resistance of
one pound, when it travelled perpendicularly to itself through
air at a velocity of 21 feet per second.
Having ascertained this point, had our tables of angular
resistance been complete, the size of the surface necessary for
any given weight would easily have been determined. Theory,
which gives the resistance of a surface opposed to the same
current in different angles, to be as the squares of the sine
of the angle of incidence, is of no use in this case; as it
appears, from the experiments of the French Academy, that in
acute angles, the resistance varies much more nearly to the
direct ratio of the sines, than as the squares of the sines
of the angles of incidence. The flight of birds will prove to
an attentive observer, that, with a concave wing apparently
parallel to the horizontal path of the bird, the same support,
and of course resistance, is obtained. And hence it appears
that, under extremely acute angles with concave surfaces, the
resistance is nearly similar in them all.
Six degrees was the most acute angle, the resistance of
which was determined by the valuable experiments of the
French Academy; and it gave 4/10 of the resistance, which the
same surface would have received from the same current when
perpendicular to itself. Hence then a superficial foot, forming
an angle of six degrees with the horizon, would, if carried
forward horizontally (as a bird in the act of skimming) with a
velocity of 23·6 feet per second, receive a pressure of 4/10 of
a pound perpendicular to itself. And if we allow the resistance
to increase as the square of the velocity, at 27·3 feet per
second it would receive a pressure of one pound.
The flight of the _corvus frugilegus_, or rook, during any part
of which it can skim at pleasure, is (from an average of many
observations) about 34·5 feet per second. The concavity of the
wing may account for the greater resistance here received, than
the experiments upon plain surfaces would indicate.
The angle made use of in the crow's wing is much more acute
than six degrees: but in the observations that will be grounded
upon these data, it may safely be stated that every foot of
such curved surface, as will be used in aërial navigation, will
receive a resistance of one pound, perpendicular to itself, when
carried through the air in an angle of six degrees with the line
of its path, at a velocity of about 34 or 35 feet per second.
The next object is to apply what has been advanced to the theory
of aërial navigation; and the following description will convey
a just idea of the best method of effecting it. Suppose a sail
to be made of thin cloth, of a firm texture, containing two
hundred square feet; and that the weight of the man and the
apparatus is 200 pounds. Then if the wind blow with a velocity
of 35 feet per second, in a certain direction, at the same time
that a cord in that direction sustains a tension of 21 lbs.
from being fixed to the machine, the whole apparatus will be
suspended in the air. But it is perfectly indifferent whether
the wind blow against the plane, or the plane be propelled by
any means against the air with an unequal velocity. Hence, if
this machine were drawn forward by the cord under a tension of
21 lbs. and with a velocity of 35 feet per second, the whole
would be suspended in an horizontal path. Now, if, instead of
this cord, any other propelling power were generated in the
same direction, and with the same intensity, an equivalent
effect would be produced, and aërial navigation accomplished.
_Vide Bishop Wilkins's Math. Magic.--Hook's Philosophical
Collections.--Sir G. Cayley on Aërial Navigation._
No. LXXVIII.
A watch to go constantly, and yet needs no other winding from the
first setting on the cord or chain, unless it be broken, requiring
no other care from one than to be now and then consulted with,
concerning the hour of the day or night; and if it be laid by a week
together, it will not err much; but the oftener looked upon, the
more exact it showeth the time of the day or night.
NOTE.
For a pocket watch it will be necessary to employ a small
balance, with a nut attached to its axis and communicating with
the fusee, the continued vibration of which will, by winding the
watch, give it nearly all the advantages of a perpetual prime
mover. Should the time-piece be placed in a fixed case it will
require a communication between the joint of the door and the
fusee, and this may likewise be readily applied to the case of a
hunting watch.
Mr. Gout's _pedometer_ not only marks the time, but the number
of paces passed over from one place to another: this is
accomplished by means of a chain or string passing to the leg
of the wearer, or to the wheel of a chariot, which is made to
advance the index hand one division at each elevation of the
foot: thus, on the same dial, exhibiting, at one view, both time
and distance. The same pedometer will, by a proper application
to the saddle, ascertain every pace a horse takes, and it may be
made to change its performance in a second, should the horse in
the course of measuring go from one pace to another.
No. LXXIX.
A way to lock all the boxes of a cabinet (though never so many) at
one time, which were, by particular keys appropriated to each lock,
opened severally, and independent the one of the other, as much as
concerneth the opening of them, and by these means cannot be left
open unawares.
NOTE.
This suggestion, which is both ingenious and useful, might be
advantageously adopted in every description of cabinet or chest
now in use; it may be performed either by cranks and wires, or
by sliding bolts and levers communicating with each lock: the
latter way, though attended with greater expense, is by far the
most durable.
Another and more simple mode offers itself in the use of a
series of spring locks, which may be closed by the pressure of
the lid, unconnected with any other mechanism.
No. LXXX.
How to make a pistol barrel no thicker than a shilling, and yet able
to endure a musket proof of powder and bullet.
NOTE.
It requires no great share of ingenuity to accomplish this
object, as an examination of modern fire-arms will fully
testify; many pocket pistols that are manufactured at the
present period, being at least as thin as those described by the
noble author.
No. LXXXI.
A comb-conveyance carrying of letters without suspicion, the head
being opened with a needle screw, drawing a spring towards one; the
comb being made but after an usual form, carried in one's pocket.
NOTE.
A pocket comb and portable spoon, as described in this and the
following article, with double sides to conceal any letter,
paper, &c. are too simple to need a particular description.
No. LXXXII.
A knife, spoon, or fork, in an usual portable case, may have the
like conveyances in their handles.
No. LXXXIII.
A rasping-mill for hartshorn, whereby a child may do the work of
half-a-dozen men, commonly taken up with that work.
NOTE.
A variety of engines have been invented for this purpose, many
of which are capable of effecting the saving of labour described
by the Marquis, as at that period (1663) the process was usually
effected by rubbing the horn or ivory over a common iron grater.
No. LXXXIV.
An instrument whereby persons, ignorant in arithmetic, may perfectly
observe numeration and subtraction of all sums and fractions.
NOTE.
Sir Samuel Morland has published a detailed account of two
instruments of this kind in a tract entitled, _The Description
and Use of two Arithmetic Instruments_, &c.--London, 1673. The
Roman _Abacus_ and Chinese _Swan-pan_ are also instruments of a
like description.
The _Abacus_ was variously contrived; that chiefly used in
European countries was made by drawing any number of parallel
lines at pleasure, at a distance from each other, equal to
twice the diameter of a _calculus_ or counter. This placed on
the lowest line, signified 1; on the second, 10; on the third,
100; on the fourth, 1000; on the fifth, 10,000; and so on. In
the spaces between the lines, the same counters signified half
of what they represented on the next superior line; viz. in the
space between the first and second lines, 5; between the second
and third, 50; between the third and fourth, 500; and so on. The
abacus was also divided cross-wise into _areolæ_, and by this
means subtractions were performed. The calculating instrument of
Mr. Babbage is however much superior to any other contrivance
yet suggested.
No. LXXXV.
A little ball, made in the shape of a plum or pear, which, being
dexterously conveyed or forced into a body's mouth, shall presently
shoot forth such, and so many bolts of each side and at both ends
as, without the owner's key, can neither be opened nor filed off,
being made of tempered steel, and as effectually locked as an iron
chest.
NOTE.
The steel fangs with which this instrument is furnished must,
like the bolt of a common latch, be chamfered from the point,
so that, on its being inserted within the teeth, the bolts
will instantaneously spring out; and no power short of the key
previously made to fit the wards of the lock will suffice to
free those who are thus ensnared. This is evidently one of those
discoveries which, though practicable in itself, appears better
calculated for swelling the catalogue of the noble Author's
inventions, than for any beneficial result likely to accrue to
the public from its discovery.
No. LXXXVI.
A chair made _à-la-mode_, and yet a stranger, being persuaded to sit
down in it, shall have immediately his arms and thighs locked up,
beyond his own power to loosen them.
NOTE.
Chairs of this description are stated to have been employed
by the monks in the darker ages of Christianity; and were
originally designed for the purpose of entrapping those who,
possessing more courage, or less of prudence than their
neighbours, ventured to penetrate the mysteries of papal
seclusion. They were formed like a common arm-chair, and
provided with two levers at the extremity of the arms; and
the same number were fixed immediately below the seat. These,
on pressing the cushion, were immediately discharged like a
man-trap: four powerful springs acting on the levers for that
purpose; and so firmly will the occupant of a chair of this
description be fixed, that it will take the united force of
four or five persons to free the prisoner. A similar chair was
exhibited at the _Villa Borghese_, Rome, in 1644--"They shew'd
us also a chayre w^{ch} catches any who sitts downe in it so as
not to be able to stir out, by certaine springs concealed in the
armes and back thereoff which at sitting downe surprizes a man
on the suddaine, locking him in by the armes or thighs, after a
true tretcherous Italian guise."--Vide _Evelyn's Memoirs_, vol.
i. p. 107.
No. LXXXVII.
A brass mould to cast candles, in which a man may make five hundred
dozen in a day, and add an ingredient to the tallow, which will make
it cheaper, and yet so that the candles shall look whiter and last
longer.
NOTE.
The usual method of dipping _store candles_ is subject to many
objections, though the expense attendant on casting those called
_moulds_ has hitherto been an impediment to their general
manufacture. A more simple method now offers itself, which is
equally advantageous and economical. A quantity of drawn tubes
being first cut into the given lengths, metal collars must then
be soldered on the extremity of each length, with an orifice of
sufficient size to allow the tallow and wick to pass through the
whole series of tubes. They must then be connected together by
a screw cut in each alternate end, and the whole, thus formed,
passed through a steam pipe of sufficient size to prevent the
tallow chilling in its passage through the moulds. When cold,
each joint of the mould must be separately unscrewed and the
candles separated by a sharp knife.
A means of purifying the tallow, and as such, of rendering the
candles whiter and more durable, likewise suggests itself in
the following simple process. The vat, or copper, containing
the melted tallow, must be provided with a shower bath placed
immediately over the surface, to which must be attached a
reservoir of cold water: this, by the action of a lever, may be
thrown through the grating of the bath, and falling upon the
tallow, will, in its passage, carry to the bottom of the vat
the whole of the carbonised animal matter and other impurities
with which it is charged. After allowing a few minutes for the
lighter fluid to rise, the water may then be drawn off, by a
cock placed at the bottom of the vat for that purpose, and the
same process repeated till the tallow is fit for use.
No. LXXXVIII.
An engine, without the least noise, knock, or use of fire, to coin
and stamp 100lbs. in an hour, by one man.
NOTE.
Antoine Boucher appears to have been the first engraver who used
the fly-press for the multiplying of metallic impressions from
an engraved matrix. This ingenious mechanic was employed by
Henry the Second of France, and the first money was struck with
it in that kingdom about the middle of the sixteenth century;
it was soon however laid aside on account of the great expense
attendant on its use, and the old method of striking with the
hammer was again resorted to. Queen Elizabeth also had milled
money coined in England about the same period; but it did not
continue for more than ten years; and it was not till 1662, that
the screw press was finally established in the mint of this
kingdom. The accelerated motion of a screw, although possessing
many advantages over the old method, does not appear fully to
answer the above description, as the noise attendant on its use
is certainly very considerable; it is probable therefore, that
the hydrostatic press, or a powerful lever worked by a crank,
was intended by the noble author as a substitute for this useful
machine.
It appears probable that the insertion of this Article
originated in an ignorance of the plan formerly proposed by
Boucher, which appears of all others best adapted for the
purpose of coining with rapidity, and which was not at that
period acted upon in England; on the discovery of which the
following Article was substituted by the noble author; and
appeared in the first printed edition of the _Century_.
No. LXXXVIII.
How to make a brazen or stone head, in the midst of a great field or
garden, so artificial and natural, that though a man speak never so
softly, and even whispers into the ear thereof, it will presently
open its mouth, and resolve the question in French, Latin, Welsh,
Irish, or English, in good terms, uttering it out of his mouth, and
then shut it until the next question be asked.
NOTE.
Albertus Magnus, a celebrated philosopher of the thirteenth
century, is said to have constructed an _automaton_ which not
only performed all the apparent motions of life, but absolutely
answered questions. It is recorded of Thomas Aquinas, that,
having accidentally seen the head, he was so terrified that he
broke it in pieces, upon which Albert exclaimed: _Periit opus
triginta annorum_! Though this appears one of the earliest
instances of a speaking automaton constructed by one of the
laity, there is no doubt but that the method of conveying
answers to various interrogatories, by the agency of concealed
pipes or a speaking trumpet, was practised at a very early
period. That the impostor Alexander, however, caused his
Æsculapius to speak in this manner is expressly related by
Lucan. He took, says this author, instead of a pipe, the gullet
of a crane, and transmitted the voice through it to the mouth of
the statue. But the invention of the _invisible girl_, which may
be considered as an improvement on the oracular responses of the
darker ages, infinitely surpassed any of those hitherto recorded.
This very ingenious apparatus was publicly exhibited both at
Bristol and in London for a considerable period, during which
time no discovery was made of its internal mechanism; and it
is probable that its construction would have remained a secret
to all but the exhibitors, but for the ingenuity of Mr. (now
Professor) Millington, who, in a course of Lectures delivered
in the winter of 1806, explained the manner in which it was
performed.
The _visible_ part of the apparatus connected with the
_invisible girl_ was thus constructed: first a mahogany frame
resembling a bedstead, having at the corners four upright posts
about five feet high, was united by a cross-rail near the top,
and two or more cross-rails near the bottom, to strengthen
the frame, which was about four feet square. The frame thus
constructed was placed upon the floor, and to the top of each
of the four pillars were attached as many strong bent brass
wires converging towards the top, where they were secured by a
crown and other ornaments. From these wires a hollow copper ball
was suspended by slight ribbons, so as to cut off all possible
communication with the frame. The globe thus supported was
supposed to contain the invisible being, as the voice apparently
proceeded from the interior of it: and for this purpose, it was
equipped with four trumpets, placed round it in a horizontal
direction, and at right angles to each other; the trumpet
mouths coming to within about half an inch of the respective
cross-rails of the frame surrounding them.