ELECTRICAL THEORY OF THE UNIVERSE.

purpose of throwing a stumbling-block in the way of Mr. Mackintosh. I trust I may be in error; for the legitimate aim of all controversy is the attainment of truth; and this aim cannot be accomplished by a subtle and ingenious system of special pleading, pressing into our service the opinions and assertions of others, not because they coincide with our own ideas, but merely because they militate against those of our opponent. But to the point.

I confess myself to be an humble individual of that humble class of reasoners, alluded to by the learned professor, who conceive that the cause of that by which sensation is affected, and a material impulse experienced, must itself be material; and that as sensation is affected by, and a material impulse experienced from electricity, the cause of electricity is corporeal; and, further, that as it possesses, in an emi nent degree, the properties of a highly elastic fluid, we humble class of reasoners must be content, in our darkness, to consider it as such, until Sir John Leslie, or some other philosopher, proves the contrary. For, after all, to what do the learned professor's observations amount? He wishes to object to and set aside a theory, not only without substituting a more satisfactory one, but without favouring us with any other! unless, indeed, the unintelligible sentence with which the extract given by Kinclaven concludes, be an attempt at such substi tution. If so, I ask Kinclaven to state candidly whether he comprehends the learned professor's meaning. It is impossible; for I think it would be no very difficult matter to prove, by the professor's own words, that he did not understand it himself. What, for instance, is the meaning of the "colour of emission!" And what the explanatton of the assertion, that the "colour is modified by the peculiar character and intensity of the retaining force? What is retained? and what force is here alluded to? To the former question, I presume the reply is, "the particles of light," which the learned professor speaks of in the same senience, as being "disengaged from the surface of the conductor." This light, then, according to the learned professor, is not the electric light. And this materially weakens his own position. For

407

if there is a retaining force, and the power of that retaining force is overcome by electricity, then the cause of elec tricity must be material; and, as the retaining force was overcome by the elasticity of that material something, I ask, whether it is more philosophical to deny, or to admit the claim of electricity to the title of a material fluid. The learned professor amuses himself at the expense of the blindness of those who 'complacently describe the play and vagaries of an electrical current whose exist ence was never proved." To this I shall not add an observation, but content myself by supposing that, at the time it was written, the new wonders of the science of electro-magnetism had not yet penetrated so far north as the modern Athens, and by assuring Kinclaven that numbers of scientific men, whose names I am not worthy to mention, will peruse the learned professor's observation with even greater complacency than their countenances assumed when they described the "vagaries of an electric current." The learned professor proceeds to state, that "we are acquainted only with electric attraction and repulsion, and with the transmission of electrical influence, and that all beyond this rests on hasty conjecture!" Now, if Kinclaven will inform us what is the transmission of the electrical influence, and how it is effected, I shall be happy, also, to reply to this. In the mean time, I may add that by far the great majority of electricians believe the phenomena of electricity to be produced by a subtle fluid, or by two fluids. And, unsatisfactory as our present theories may appear to be, we must be content with them until a more satisfactory theory is framed.

I beg leave to assure Kinclaven that these observations are not the result of any wish to take a part in the controversy respecting Mr. Mackintosh's theory; believing, as I do, that, in nine cases out of ten, controversy tends rather to retard than to advance the true interests of science. I have, and trust I ever shall keep, but one object in view-the attainment of truth.

Before I draw this letter to a close, I may congratulate myself, in being able to unite with Kinclaven, in his admiration of our great NEWгON. He, at least,

Kinclaven will readily admit, was a man not given to "hasty conjecture." I cannot, therefore, more appropriately conclude this tedious communication than by referring him to Newton's " Optics," (8vo. edit., pp. 324 and 327,) by a perusal of which he will learn it was the opinion of that philosopher, that electric bodies, when excited, emitted an elastic fluid.

Yours, &c.

WILLIAM LEITHEAD.

22, Compton-street, Brunswick-square 12th September, 1836.

IMPRACTICABILITY OF AERIAL NAVIGA-
TION- MONTGOLFIER'S PREFERABLE
TO GAS BALLOONS.

Sir,-The subject of aerostation has
been more fully and better discussed in
your periodical than in any other; but
although your intelligent correspondents
have, during the last twelve years, sup-
plied you with numerous observations
and ideas on the subject, nothing essen-
tially new or important has been elicited,
This comes from the sterile nature of the
thing itself. No one, as the homely say-
ing is, can "make a silk purse out of a
sow's ear." It is quite astonishing to ob-
serve how so many men of good sense
can talk of propelling and directing a
balloon through the air, on principles
derived from the way of a ship on the
sea!" A vessel either on or in a mass of
water can be propelled even against a
current of that water, because the density
of the medium allows of a power being
applied of a velocity within the reach of
our physical organs to produce. But for
a power to be applied (in an analogous
way) in the car of a balloon, against the
air, in which the whole machine is im-
mersed, it must have six hundred times
the velocity of the stroke which will pro-
duce the same effect upon the water.
Some persons say, 66 we will take up a
steam-engine," &c. But the more weight
you take up, the greater must be the
dimensions of your balloon! After all-
for it is loss of time to argue such a
matter-it is evident that no power can
draw a balloon against the slightest
zephyr, but one which would place the
car and the balloon on an horizontal line
together, like a horse drawing a cart!
With regard to the elongated and fish-

like shapes that have been so often proposed, the fallacy is still more afflicting. When there is no power of propulsion through the fluid, how can the position of the elongated body be decided? Even a barge going down a river along with the stream has not the least power of steerage by the rudder, because it does. not go through the water, but with it: without external power applied, either of traction, oars, or wind, it goes along sideways, or any way, just as it may happen. Another fallacy in the ideas connected with an elongated fish-like balloon, is also of a serious nature, setting aside the physical impossibility of propelling it. How is it to be kept in a horizontal position? A balloon of such a shape (like Egg's, the Pall-Mall gunsmith, or of Col. Lennox's "Aerial Ship"), being filled with gas and set up without any load, would certainly be liable to rise in any way but the one desired. If to prevent its bursting by the expansion of the gas, it were only three quarters or two-thirds full, it is ten to one but that it would rise up endways. If a net, car, &c. were to be attached to it, with a load of passengers, it would double up into the shape of a crescent; that is, if the gas did not rush to one end (which is most likely), and so defeat all the fishlike calculations of the constructors! A stout back bone to the fish-balloon might prevent the doubling up I speak of, but it would not save it from the chance of going up end ways, much to the inconve nience of the travellers in the car beneath. But it is absolute waste of time to dwell on such nonsense. It is a pretty thing to see a balloon ascend when you are near it at the time, and will answer the pur poses of the proprietors of public gardens, &c. The near view of any large mass in motion, such as a ship launched, a huge tree falling, &c. convey a novel and peculiar feeling to our senses.

In 1810, Madam Blanchard, the widow of Blanchard who, with an Englishman, crossed in a balloon from Dover to Calais, arrived at Naples with her balloon. An ascent was ordered by the King (Murat) to take place from the Campo Marte, on an occasion when there was to be a grand review of troops. In consequence of my known chemical propensities, the King 'ordered the talented Giovanni Dall' Arini and myself to make all the preparations,

AEROSTATION.

410 MR. GREEN'S ACCOUNT OF THE ASCENT OF THE GRAND BALLOON.

ends. Such a vessel charged with one
hundred cubic feet of the best gas, might
easily be fitted into the bottom of a large
cask. The empty balloon being placed
over it, and communicating by a tube and
stop-cock. In the same cask might be
arranged a long cord of the lightest and
best materials. The whole apparatus,
properly made and packed, would always
be ready on deck like a mere water-cask.
The balloon once up, by adding more
rope to the thin one belonging to it,
must come at last into contact with the
edge of a cliff, or with the surface of any
lee-shore. The balloon might also be
made to take up a small grappling, com-
posed of three or four shark-hooks tied
back to back. I fear, however, that there
would be considerable risk of the bal-
loon's being torn by the yards, &c. of
the ship before it could be got clear of it.
In the case of a low coast without cliffs
or high rocks, an empty water-cask, pro-
tected by sacking, &c. would take a line
on shore as well as a balloon. Apropos of
water-casks and provision-casks, I have
suggested many years ago, that if, as
these become empty, they were to be
bunged up and stowed so as not to be
washed away, their buoyancy would pre-
vent the vessel from sinking even when
she were full of water. All the trouble
is in well bunging up the casks when
they become empty.
Yours, &c.

September 10, 1836.

F. MACERONI.

MR. GREEN'S ACCOUNT OF THE ASCENT OF
THE GRAND BALLOON FROM VAUXHALL.

The inflation of the balloon commenced at 10 minutes past 11, on Tuesday, September 9th, and in the space of 12 minutes it possessed sufficient power to support itself. Thirty-six men of the Lambeth division of police were then placed around, each taking charge of one of the cords connected with the network. In about an hour an iron weight of 561b., provided for the purpose, was also attached to each cord, and shortly after five more at different parts, making in all 41 weights of 561b. each. These were soon all lifted three feet from the ground, and the policemen were obliged to pass their staves through several of the meshes to prevent the cords cutting their hands. This enormous combined resistance was found insufficient, and 20

of the workmen in the gardens were called to the assistance of the police. The rain now fell in torrents, and the netting and silk must have absorbed at a moderate calculation 300lb. weight of water, besides the quantity retained on the top of the balloon by the pressure of the net on the silk, each mesh forming a small reservoir. At a quarter past four the inflation was completed, having occu pied, and under these unfavourable circumstances, only five hours and five minutes. I had supposed five hours would have been the time required, but I now believe four would be sufficient on

a sunny day. The process of attaching the car to the net was commenced, and, from the shrinking of the ropes by the wet, and the necessary adjustment required at the first ascent (which cannot be done until the balloon is inflated), was I fear somewhat tedious to the company, but the ropes being now cut to the proper lengths, this will be for the future effected very quickly. Twenty-four bags of ballast, weighing together 400 b., being placed in the bottom of the car, my companions, with the greatest alacrity, obeyed my summons, and took their seats; they were Mr. Hildyard, Captain Currie, Mr. Holland, Mrs. Green, Miss Green, Mr. E. Gye and Mr. W. Hughes (sons of the proprietors), and Mr. James Green, my brother, making in all nine persons, myself included.

I had calculated the power of the balloon according to the average specific gravity of the gas made by the different companies, and found it to be consider ably more than has been stated in the advertisements; but it was the wish of the proprietors and myself to underrate, rather than overrate, its capabilities, in order that the public should in no case be disappointed, but, on the contrary, unless some unforeseen circum. stances occurred, be surprised. However, owing to the exertions made by Mr. Hutchinson, engineer to the London Gas Company, and his judicious arrangements in the manufacture of the gas, even my own expectations were surpassed, and I was obliged to allow about 15,000 feet of gas (equal to onefifth power of the whole) to escape before I could release the machine from the moorings, the ascending power being much too great, and no room being left in the car for many more passengers.

THE HOUSE-BURNING SYSTEM.