bers, say a 50-horse power in lieu of the 60-horse power on the former plan. This cannot be proved without a complicate diagram, and an explanation that would obtrude too much upon your pages, and most probably on the patience of your readers on the present occasion.

This will enable us either to add 5,000 more to the cargo, or, by using a 60-horse engine, to go with more speed.

Many persons erroneously suppose that any propelling force of wattage, when acting in the direction of the car, will not tend to propel the balloon above it. Let A, fig. 1, plate 3, be a balloon; let B be the position of its car, propelled beyond its centre of suspension, A, by any given power of waftage. Draw A C perpendicular, and CB parallel to the horizon; and let these lines be made in the same ratio to each other as the weight of the car is to the propelling, power; then the line AB will represent the whole action of the car upon the balloon. Draw AD and BD respectively parallel to the two former lines; and as the floatage of the balloon is equal to the weight of the car, BD will as truly represent the floatage as AC does the weight; and, as the propelling power is, as soon as the speed becomes uniform, equal to the resistance, being the cause and measure of it, A D must as truly represent the resistance as its equal CB does that of the propelling power. In this position, then, all the powers are balanced in equilibrio; but there will be no resistance till the balloon has the velocity necessary to generate it, and this it finds at the same speed in the line A D, as if it were mov. ing along its equal C B.

I will here take advantage of the same diagram to observe, that if a balloon be supposed to be at anchor in a gale of wind, by the car being secured to the ground, and the line AD be taken to represent the force of the wind, and BD the power of floatage, then A B will be the position the cordage will fall back to. The resistance to the prow of the balloon in question, at a hurricane of 60 miles per hour, would be about 20,000lbs.-deducting the car then on the ground, its floatage would be about 63,000-so that it would fall back about one part in three, which are the proportions purposely taken in the diagram, in order to prove that permanently-filled balloons would ride out

storms when properly secured, without the danger of being driven to the earth and damaged.

The

Some persons are, however, disposed to strike at the root of all discussion as to steering balloons, by affirming that no waftage can propel bodies suspended in one and the same element in which the waftage takes place. These persons I will refer to p. 172 of Nicholson'e Chemical Journal for 1809, where they will find a description of a small machine, which they can make for themselves in a few minutes, that will elevate its own weight from the table to the ceiling, merely by the waftage it creates. machine I have there described is a mere toy, but the principle on which it acts is capable of the most powerful and extensive application. I send you a view of its application to driving balloons, copied from a paper of mine at p. 81 of the Philosophical Magazine for 1817 (see plate 2, fig. 1), where there is likewise given a side elevation of a balloon with oblique wing waftage (fig. 2). The former by vanes revolving on an axis, the other by the heeling up and down of the surfaces in a reciprocating action, as in the bird's wing.

There is in one of the early volumes of the Philosophical Transactions, an account of propelling a boat with considerable velocity by men working this sort of waftage against the air; but I should prefer trying the more uniform action of the oblique vanes. More than one may be used on the same axis; and they may be so constructed as readily to apply their power, either to propel or retard, elevate or depress, as occasion may momentarily require. This will be obvious on inspecting fig. 2, plate 3.

Let the power of the engine communicate opposite movements to the reversed sets of fliers, C and D, through the cylindrical shaft A, and the wheels connecting them; the whole free power of the waftage will act in the line of their axis of motion. Conceive this axis to be moved into any position with respect to the horizon, by turning the hollow mast B (by which, through a suitable collar or socket the apparatus is supported from the car), and the balloon will be propelled accordingly. In the balloon we have been estimating, the four sets of such fliers would have to be 10 yards in mast or radius; and each sail would contain 30

square yards of surface. The figure given is intended merely to explain the principle of this action in the most distinct manner. In practice, this fabric, to unite strength with lightness, would be braced like the masts and sails of a boat; and its main strength derived from the ropes or metallic rods forming three braces.

Communicating centrifugal force to air by means of a hollow drum and fans worked by the steam-engine, is another means of getting a propelling power conveniently applicable in every direction that may be required; for by having a moveable mouth-piece, from which the air escapes, the re-action will always be in the opposite direction. Though convenient in this respect, it is too wasteful of power to be used for balloons, unless for small experimental purposes. Many other considerations remain untouched, upon; but I have already obtruded too much upon your pages with these dry details. The subject, however, is one of great interest, not merely in a mechanical point of view, but as to its stupendous effects on mankind at large; civilisation and, I trust, perpetual peace are in its train of consequences.

To such as have honoured me by wading through the train of this investigation, I will beg to remark, that they must not blame me for wilfully introducing such acres of cloth to their notice. Calculation from well-known data proves that balloons can only be driven with sufficient speed to be useful on the scale of magnitude I have pointed out. Let the question be put where it truly rests, whether such fabrics can or cannot be made and managed. The case is one evidently too great for individuals to make efficient experiments upon; and I am glad to see that some of your correspondents have recommended a subscription purse, and I hope that plan may be followed up. I proposed this in the year 1817, in the following terms (page 28, yol. 1., Philosophical Magazine):—

"We, the undersigned parties, enter into the following subscription for the purpose of ascertaining how far the principle of balloons supporting heavy burthens in the air may be made useful as a means of conveyance.

"No person to be called upon for his subscription money till at least 10001. be subscribed for.

"When the subscription has reached this

amount, an annual Committee of seven of the subscribers to be elected. Every subscriber of 1., and of less than 57., to have one vote. Subscribers of 51. to have two votes; and subscribers of larger sums to have one additional vote for every additional 51. they subscribe.

"No experiments to be undertaken but by order of the Committee, who may call in the advice of such civil engineers as they chose to consult.

"An annual report of the application of the funds, and the result of the experiments made, to be printed for the use of the sub

scribers.

These regulations being the basis on which the subscription is made, cannot be altered; but subsequent rules not militating against these, may be entered into at a general meeting of the subscribers expressly convened for the purpose."

The late Mr. Lovel Edgeworth immediately before his death became a suh scriber of 507. towards this fund, which his deservedly celebrated daughter subsequently offered to make good. Mr. Evans also became a subscriber; but the age was not then ripe for the subject-steam-boats were in their infancy, and railroad velocity unknown; twenty miles an hour then seemed monstrous and chimerical; now our only fear is that balloons will not have speed enough to satisfy our locomotive mania. I must not mention the respected name of Edgeworth without stating that he puts in a previous claim to that of Mr. Evans (see Philosophical Magazine, for 1816, p. 185,) to the principle of steer ing balloons on the tacking plan by the use of the inclined plain. He appears to have communicated the plan to Monsieur Mr. 1782. Montgolfier in the year Evans is, however, the first person that has proved the invention experimentally.

Balloons, as has been long ago observed, ought not to be made all in one, but have several departments for the gas, like "the stomach of a leech,"-aud should the promoters of aerial navigation get up a purse and combine their efforts during the present season, I should strongly recommend that Mr. Green's large balloon, and that gentleman's great experience and skill, be put in requisition; that two other of the largest balloons that are in town be packed at opposite sides of this large one, under one netting made in compartments for the purpose; the whole free floatage may then be ex

pected to be equal at least to 23 men; let the crew be Mr. Green and his assistant, and let the weight of twenty-three men, say 3400 lbs., be occupied by the lightest possible tubular boiler and highpressure steam-engine of 5-horse power, which, no doubt, would be got up with a 4-hours load, at 2500lbs., leaving 1100 lbs. as the weight of the fliers for waftage. This might be expected to drive the balloons at from seven to eight miles per hour, which would be quite sufficient as a first experiment.

As men have the choice of time, in a great degree, those winds that are tolerably favourable to any intended voyage, can often be selected; different current in the air can also be occasionally met with, so that balloons offer more advantages from the wind, than inconvenience from its occasionally being too strongly against their line of sailing.

I have been applied to by an ingenious foreign mechanic, now in Rome, who affirms, that by a particular apparatus of his own, he has guided small balloons with considerable velocity; that he is in possession of an engine four-times more energetic, weight for weight, than the lightest of our steam-engines (the powers of which I gave him, as stated in this letter), and that he wishes much to exhibit the proof of what he says, in London, should he meet with any persons who would pay the expenses of his journey; previous to which, he offers to satisfy any of the British residents in Rome that he can perform what he asserts. Should a good subscription-purse be obtained for general ballooning purposes, it may be just and desirable to give this humble workman an opportunity of substantiating his claims, by thus previously exhibiting his machine to the celebratep artists, Mr. Gibson and Mr. Macdonald, or other well-known British residents in Rome. For my own part, I shall be ready to become a subscriber to any rational plan for trying experimen's upon balloons on truly scientific principles, and free from any jobbing or exhibition-making speculations.

Let the friends of aerial navigation be called together by advertisement in your pages, at the instigation of a few names favourable to the project; let a placesay the Adelaide Gallery, if the proprietors permit it- and some convenient day in next month, be named;

and from this meeting let such resolu tions emanate, as may best ensure the progress of The Society for Promoting Aerial Navigation.

I am, Sir,

Your obliged and obedient servant, GEORGE CAYLEY.

Forwarded Jan. 23, 1837.

AEROSTATION.

Sir,-My thanks are due to Mr Lake, for the pains he has taken to correct an error into which it appears I had fallen, in an article published in your 637th Number, on the practicability of guiding and directing air-balloons. I know it is usual occasionally when a palpable blunder appears, to take shelter behind the printer's devil, by representing it as a typographical error; however, on the present occasion, I have no desire to interpose this shield, but will readily admit that it might possibly have been so stated in the manuscript, although with Mr. Lake, I cannot "imagine how I could make so great a mistake in so simple a calculation." A mistake it certainly is ; and as Mr. Lake, I dare say, will readily allow me the credit of the blunder, I am willing to repay his courtesy by conceding to him the honour of having corrected it. Mr. Lake thinks it seems that the strength of a hundred eagles or so, would be as nothing if applied to overcome the great resistance opposed to the progress of a balloon against the wind, but thinks that great power might be gained from an air-pump. Well, if Mr. Lake likes the air-pump better, I have no objection. But afterwards, seeming to forget himself, he breaks out into the grandiloquent style and says,

"we see

the eagle possessed of power, not merely sufficient to raise its ponderous body from the earth, but also giving it a velocity outstripping the wings of the wind." Therefore, says Mr. Lake, eagles would be of no use whatever.

Farther on he says, "the effect (that is of the aforesaid air-pump) would be so certain, and the means of applying it so simple and easy, as to leave comparison with any method already known out of the question." Those who understand the subject, will not be disposed to entertain any doubts as to the effect, I believe, looking at the means proposed; but "the effect" would be of a very dif

their numbers, but with the effect of puzzling the matter more than if the details sought had been still left to the vague conjecture of individuals.

Notwithstanding these drawbacks, however, of whose importance he seems to be pretty well aware, Mr. M'Culloch, the well-known lecturer on Political Economy, and author of the "Dictionary of Commerce," and several other works of the same complexion, has thought the present a fit and proper time for putting forth a new "Statistical Survey of the British Empire."* It must be acknowledged that a standard work on the condition of the United Kingdom has been for a long time one of the most crying of our literary desiderata,-but we are by no means so well satisfied that the method adopted by Mr. M'Culloch is the proper one for filling up the vacuum so completely as it ought to be. After remarking in his preface, that the work of Chamberlayne, published in the reign of George the Second, was the last of the kind of any authority, he goes on to observe, that “during the long interval between Sir William Petty and Dr. Beeke, statistical science could scarcely be said to exist," but that, much information having been given in the Censuses of 1821 and 1832, and in the recent Reports of Parliamentary Committees and Crown Commissioners, "the time seemed to be at length arrived when it might be attempted to compile a work that should give a pretty fair representation of the present condition of the United Kingdom." Here we join issue. The grand work that is to take its place as the standard Picture of Great Britain will derive a good deal of assistance, of course, from the (too) large accumulation of raw material contained in the Parliamentary Reports, but its foundation must be laid on the basis of ORIGINAL RESEARCH, and not a stone used in the superstructure from the mass so temptingly at hand, until its trustworthiness has been tested by actual experiment. In other words, the authors of such a work must see with their own eyes, and make use of the population and other returns only so far as they tally with

* A Statistical Account of the British Empire, exhibiting its Extent, Physical Capacities, Population, Industry, and Civil and Religious Institutions. By J. R. M'Culloch, Esq. Assisted by numerous Contributors. In 2 vols. London, 1837. C. Knight and Co. 8vo., pp. 642-700.

the results of actual observation. Mr. McCulloch, it will be seen, does not think this troublesome process necessary. His work is entirely and altogether a compilation-a book made up of scraps from other books, without the writer's troubling himself to walk half-a-dozen steps from his library to ascertain from a peep at the out-of-doors-world whether any feature of the picture he was drawing of it was like or no: in short, a book where every thing is taken upon trust, and no addition made to the general stock of information. It is not a work so got up that will definitively fill up the aching void" which is generally admitted to exist.

66

The plan followed is nearly the same as that of Peuchet, in his " Statistique Elementaire de la France," relieved a little of its excessive dryness,-for, strange to say, on dry subjects our usually lively neighbours approach to the proverbial aridity of a lime-burner's basket." Our author says on this head,

"We have not been satisfied, for example, in giving an account of any branch of industry, with stating the value of its products, the number and wages of the people engaged in it, and so forth; but have, in addition, given some notices of its history, and of the more prominent circumstances that have accelerated or retarded its progress. This seemed to be necessary to impart interest to the work, to make it useful, and to give it a chance for getting into circulation."

A rather strange confession to be made by a statistician,—a dealer in nothing but mere figures, amounting, as it does, to an admission that his own peculiar department is without either interest or utility, and (which is most to the point, and doubtless true enough,) without saleability. Most readers will be perfectly ready to concur in the whole of this candid estimate of the value of bare "statistical science," per se.

The work opens with a general view of the "Extent, Physical Circumstances, and Civil Divisions of the British Empire;" the first chapter, subdivided into various sections, being devoted to England and Wales. This geographical portion is well executed, and appears to be a sort of abridgment of that part of the " Library of Useful Knowledge devoted to 66 Physical Geography "-a subject on which many numbers of that series have recently appeared. Nor is