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trical theory of the universe. It is, he says, no where stated to be in accordance with Kepler's laws," &c. I shall quote the passage I alluded to, which is given in No. 645, p. 233 :

We have no data whatever which would enable us even to attempt to fix the time occupied in accomplishing these vast operations of nature; each specific change in bodies of such immense magnitude must require periods of vast duration-compared with which the age of human records is but as one day. We are assured by experiment that the attractive and repulsive forces of electricity follow the same law as to its intensity, that is, the inverse law of the squares of the distances. Let this be compared with the laws of Kepler, and we think that the conclusion cannot be resisted, that the motion and distances of the planets are regulated and determined by this powerful and all-pervading agent.'

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I certainly thought, and I think so still, that Mr. Mackintosh meant to infer, that the effect produced by the agency of electricity would produce a similar result in the motion of the planets to that which is said to be produced by Kepler's laws. Mr. Mackintosh, however, now thinks proper to deny this. But Mr. Mackintosh must be aware that Newton has rigidly demonstrated the truths of Kepler's laws, and that they form three strong pillars in support of the Newtonian system of the universe; so that if the

A few sparks perhaps will fly off from the sun after the collision, which will afterwards be manufactured into so many comets, and they will in proper time be converted into regular planets, taking their proper places in the system in rear of the Herschel planet. Now here I cannot help remarking, that Mr. Mackintosh's theory has some resemblance to what is commonly styled the fanciful theory of Buffon.

Mr. Mackintosh seems to think that his theory derives great support from the established fact of the moon's secular acceleration. That the motion of the moon for some thousand years back has been continually accelerated, is an undeniable fact; but I am afraid it will add little in support of the electrical theory. Halley, by comparing the ancient Chaldean observations with those of the Alexandrian, and those of the Alexandrian with the Arabian, and, lastly, the Arabian with those of modern times, discovered that the moon's mean motion was a little acce.

lerated, amounting to eleven seconds in a hundred years; and how to account for this perplexing fact upon the principles of universal gravitation, resisted the united efforts of some of the greatest astronomers. La Place at last discovered the cause of this seeming anomaly in a dissertation he read to the Royal Academy of Science in 1785. He there shows

electrical theory is at variance with Kep." that the acceleration of the moon's

ler's laws, it is equally so with the Newtonian system. Then, Mr. Mackintosh, on this head we understand one another.

Again, Mr. Mackintosh informs me, that if I will examine his system more attentively, I will perceive," that so far from the momentuin of the planets being extinguished, they are supposed to be accelerated; because it is assumed they move in spiral orbits, which (the orbits being elliptic) is the same in effect as if they were rolled down an undulatory inclined plane." I beg to assure Mr. Mackintosh that I have duly considered all this, which is deducible from the equation dv2=DV2, that is, if D and V2 be constant, and d a variable diminishing quantity, and..v will continually increase. But what becomes of the momentum when the planet comes in collision with the sun? It will produce an increased velocity in the sun, and both will then move on with the same velocity.

mean motion necessarily arises from a small change in the eccentricity of the earth's orbit round the sun, which is now diminishing, and will continue to diminish for many centuries by the mutual gravitation of the planets." He determined the diminution in a century to be 11·135 seconds; he had previously de termined that a like anomaly took place in the satellites of Jupiter," and as the motions of these bodies are so rapid, in the course of a few years many synodical periods are accomplished, in which the perturbations, thus arising from their mutual actions, return again in the same order." And such synodical periods have been since verified by actual observations. La Place's great rival, Lagrange, arrived at a similar result, and demonstrated that all these small perturbations go through all their varieties, swelling to a maximum and then dininishing to 0. These great astronomers have also de

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monstrated, that the primary planets have no secular equations; that the axis major of all their orbits will for ever remain the same in magnitude; and that all the perturbations that are observed or can exist in this system are periodical, and are compensated in opposite points of every period, and that the mean distances and mean periods of rotation round their respective orbits are for ever the same.

The precision of the equinoxes was a complete mystery to Copernicus, Tycho Brahe, and Kepler. But the penetrating eye of Newton soon discovered that it was one of the perturba tions that tended to give an eternal stability to the system. La Place has demonstrated that gravity darts its influence more than fifty million times faster than light, and "sets for ever at rest the various speculative attempts to explain the cause of attraction by the agency of certain mechanical intermedia, and proves it to be a primordeal and ultimate principle ordained by the wisdom of the Supreme Architect,"

But I will ask Mr. Mackintosh, is he certain of the existence of an electrical

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fluid? He must know that we ought never to admit as the cause of a phenomenon any thing of which we do not know the existence,"

Sir John Leslie, in treating on the subject of electricity, concludes with the following remarkable observations:

"It must indeed be confessed, that after all the progress which electricity and its younger branch, galvanism, have made, the hypotheses commonly received are exceedingly vague and unphilosophical." **"In cultivating these attractive sciences, experi menters would seem to satisfy themselves with the exercise of a lower and humbler species of reasoning."**"It is rather amusing to observe the complacency with which some ingenious persons describe the play and vagaries of an electrical current whose existence was never proved.” **“We are acquainted only with electric attraction and repulsion, and with the transmission of electrical influence."**"All beyond these elementary principles rests on hasty conjecture." *** Instead of adopting one or two fluids, it were safer to suspend the assumption of any."**"We can perceive no distinctive marks of the operation of a fluid which is often confounded with the mere luminous tract occasioned by the particles of light disengaged from the substance of the

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Sir,-Having seen in your 680th Number a letter bearing the title of a New Theory of the Tides," and considering that from M'Laurin downward the same principles have been more or less elaborately explained, I confess that the novelty does not discover itself to me; at the same time it must be admitted, that one may invent what is not new. furtherance of the very general desire which appears to exist of coming to a satisfactory elucidation of the apparently uncaused tide, viz. that on the remoter hemisphere of the earth during the conjunction, &c. of the sun and moon, I will enter upon your appropriate pages, with your leave, the mention of another possible, not to say necessary, element, as greatly auxiliary to the determination of the question. This is a body which recedes beyond, or approaches within, the average distance of our atmophere's extension from the surface of the earth, according to its position with respect to those luminaries; for, being an encompassing sphere to the air, as that diaphanous fluid is to this globe, the confluence of its particles will be similar to the confluence of the tidal air, by which it is inflated and separated from the terraqueous surface.

The approximation of this orb-the sky will therefore always take place where the least direct effect from the sun and moon leaves for a time a shallow atmo. sphere between it and inferior ocean; the tide whereof is raised by the tendency of bulk towards bulk in the passing of the fluent masses: which will resolve the difficult case, to even Newtonian mathematicians, that of the remoter tide exceeding sometimes the height of the illumined tide. Should it be asked, how

is the existence of such a capacious shell of translucent matter discerned or proved?

its colour is distinctly azure, varying according to the presence and position of the sun, and by its tone of increased depth towards the zenith, where the air is of least gauge to a spectator, it is manifest that atmosphere, a transparent firmament, is interposed to conduct, not originate; if to qualify the hues by extraneous floating particles of moisture, rather than by a property at variance with its fitness as medium of all rays to recipient vision. Its form is necessarily such as the atmosphere's which it bounds, and its gyration probably very rapid. Other benefits resulting from so stupendous an appendage to this planet may be inferred; amongst which, a similar protection from solar power to that which shining Venus analogously enjoys may not be overlooked.

Some have justified the confounding of air and sky, in assuming that the blue dome is an appearance which results from the darkness of outward space as seen through the enlightened atmosphere; but the privation of light cannot be reflected, and if we regard the mountain sky and the embosomed lake, the eye is equally delighted with the cerulean tint, not shocked by a refulgent blaze of brightness (white light unmodified) beaten back to us from the serene expanded mirror.

I am, Sir,
Yours respectfully,

W. F. G. WALDRON. Upper Holloway, Aug. 23, 1836.

BALLOONS AS NOW CONSTRUCTED. Balloons are bags of a spherical or sphe roidal form, made of gores of silk, coated with a varnish which renders it impervious to air. The best for this purpose is made of caoutchouc. Each of the gores is prolonged into a rectangular strip, and these, when sewed together, form a long cylindric tube. The air having been forced from the balloon by compressing it, this tube is tied to that which is adapted to the inverted barrel, the counterpoise being removed, and the pressure, if necessary, aided by loading the gasometer with weights, the contained gas, with that which is subsequently generated in the barrels, is forced into the balloon until it is completely inflated.

Hydrogen gas having not more than th

of the density of atmospheric air, the joint weight of a large balloon and the gas which it contains, is far less than an equal bulk of atmospheric air; and it will not only rise itself, but will carry with it a considerable additional weight. In order to attach a weight to it, a net-work is formed of cords in such manner as to embrace the upper half of the inflated balloon, and from its equator, straight cords proceed, to which a car is tied. The balloon must be of such size as not only to carry up the persons who are to mount, with their necessary equipment, but also a considerable quantity of ballast. This is in the form of sand tied up in canvas bags. The object of this combined with a valve in the top of the balloon, is to enable the aeronaut to ascend or descend at pleasure, as long as the ballast and the gas in the balloon are not wholly expended.

This valve is placed on the top of the balloon, and is thus constructed: the gores, instead of meeting in a point, are united upon a ring of whalebone, and thus leave a circular opening; to this a circular shutter of silk, spread upon a similar ring, is adapted by a hinge; two cords proceed from this, over the net-work, in opposite directions to the car; by one of these the valve can be opened, and by the other, closed.

Then the balloon is released by cutting cords which held it down, the tube which proceeds from its lower point, and is long enough to reach the car, is left open, in order that the gas in the balloon may be at liberty to escape as it tends to expand itself, in consequence of its reaching regions in the atmosphere less dense than those nearer the surface of the earth. Although the escape of this gas renders the balloon somewhat lighter, it must finally reach a position where its weight is exactly the same as that of an equal bulk of the surrounding air, and must cease to ascend. A farther height may be attained by throwing out ballast. This is done by opening the bags in which it is contained.

When it is wished to descend, the valve in the top of the balloon is opened until the collapse caused by the escape of the gas renders the balloon heavier than an equal bulk of the surrounding medium, and the force which causes the descent will be an increas. ing one, as the collapse is increased by the increasing pressure of the denser air. It may therefore be necessary to check it by the dis-, charge of ballast, and by doing this in suffi cient quantity, the balloon may be rendered stationary or caused to ascend again. In the latter case it is no longer necessary to allow the gas to escape by the tube beneath, which is therefore closed by knotting it.

A balloon has no other capacity of being

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directed except in ascent and descent. No power has yet been discovered, which can be called into action, of sufficient intensity to propel a balloon through the air, and make it move in a direction contrary to the currents of wind, and which shall be produced by apparatus sufficiently light to be carried up by a balloon-Professor Renwick's Lec

tures.

NOTES AND NOTICES.

Writings of Roger Bacon.-The Academie des Sciences Morales et Politiques was on Saturday informed by M. Cousin, that he had just discovered some manuscripts which are important to scholastic and philosophic history. They are writings of Roger Bacon, the celebrated philosopher of the 13th century. Roger Bacon was an Englishman' by birth, but passed nearly the whole of his life in France. He became a Franciscan friar, and lived. a long time in the convent of the Cordeliers, to which he was confined by order of the General of the Franciscans. This, notwithstanding the silence of Montfaucon and the other bibliographs, induced M. Cousin to believe that there must be manuscripts by Roger Bacon still existing in France. He began by making searches at Douai and St. Omer, where there were formerly English Colleges. These searches have been successful. The only work of Roger Bacon hitherto known is his first letter to Pope Clement IV., which Bacon entitled Opus Majus. Clement IV., who protected Bacon, desired that he' would give him an exposition of the state of science in the 13th century. Bacon, receiving no answer to his first letter, addressed a new work to the same Pope, under the title of Opus Minus. The second letter also reniaining unanswered, Bacon remo lelled his work, and addressed a third letter to the Pope, which he called Opus Tertium. The Opus Majus was published at London in 1733. England possesses a manuscript of the Opus Minus, and it has hitherto been believed that there was no other in existence; but M. Cousin has discovered at Douai a manuscript containing a considerable fragment of it. This work, in his opinion, is of no great importance. It is not, however, the same with the Opus Tertium, which may be considered as the last words of Roger Bacon; a manuscript of which has been discovered by M. Cousin, and is the only copy to be found in France. He has, besides, recently discovered at Amiens another manuscript by Bacon, the existence of which had never been suspected. It contains questions on the physics and metaphysics of Aristotle. These three manuscripts, of which M. Cousin is preparing a memorial, will throw a light upon the history of scholastic philosophy, and inform us whether or not Roger Bacon was really, as has been asserted, the inventor of the telescope, the microscope, and gunpowder, This is a question which, for want of authentic documents, it has hitherto been impossible to solve.-French Paper.

Porcelain Colours.-Tue pink colour which ornaments the English porcelain has been hitherto unknown in France, and when require in that country was always bought here. M. Mallagutti, of the manufactory of Sevres, has analyse this colour till he is now able to compose it. In the course of his experiments he discovered another colour similar to crimson lake, which is much more durable than any derived from the animal kingdom, and which may be advantageously employed in oil-painting.

The Meteorological Society of London is about to be revived, after having lain dormant for several years, not from the lack of pecuniary means to carry into effect the object of the Society (as nearly 1007, have been invested in the Three per Cent.

Con ol), but from a want of that union of purp se and harmony of operation which ought to charac terize every public body. A portion of the above fund is to be dvoted to two prizes of, 50%, and 25%. respectively, for the first and second e-says on a given meteorological subject. A meeting of the present members will be called, by public advertisement, in a very short time, when gentlemen friendly to meteorological science will do well to become members without delay. Dr. Birkbeck is the President of the Society; Dr. Clutterbuck, Professor Daniells (King's College), Dr. Shearman, and many other scientific men, are among the members.-From a Correspondent.

Carriage-Speed Regulator.--An ingenious plan has been forme i to stop waggons, coaches, and other carriages, which my have been run away with by horses. It is simply to apply the governor used to steam-engines, so as to bring the break into opera

tion.

Botanical Society of London.-A number of botanists, amateurs, &c. have recently held several meetings at the Crown and Anchor Tavern, Strand, fer the purpose of forming themselves into a Society, bearing the above title. One striking fratare of this Society is, that ladies will be admitted members; this we think highly deserving of commendation, as many ladies are not only excellent b tanists, but they can generally devote a considerable portion of time daily to practical botany, Among the leading objects the Society propose are the following:-The advancement of botanical science in general; the particular cultivation of descriptive and systematic botany; the formation of a library, herbarium, and museum; the reading of original paper, extracts, and tran-lations; the exchange of s ecimens with other societies or individual collectors; and every other available means that may promote the object of the Society, It is further intended that the Society shall consist of the following classes of members; viz. resident, corresponding, honorary, and life members. We are glad to fini, among the mighty mass of bricks and mortar, ladies and gentlemen so ardently de voted to so healthy and endea ing a pursuit as botany. We shall be happy to hear of their com plete success.

Wire for Musical Instruments. — - Sir, Admir ing much the toues of the newly-invented musical instrument, the Seraphine, I endeavoured to construct one, and have succeeded in accom plishing the task; but find great disappointment in its not keeping in tune. In making the tongues, or vibrato:s, I have tried both brass and Ger man silver; the latter producing the finest tones, but subject to the before-named defect. If any of your intelligent correspondents could point out the best metal to articulate quick, and stand in tune, and sufficiently flexible as not to be liable to break with the pressure of air during its vibration, and also where it can be purchase, he would much oblige, A MECHANIC. August 30, 1836.

British and Foreign Patents taken out with economy and despatch; Specifications, Dis. elaimers, and Amendments, prepared or revised; Caveats entered; and generally every Branch of Patent Business promptly transacted.

LONDON: Published by J. CUNNINGHAM, at the Mechanics Magazine Office, No. 6, Peterborough-court, between 135 and 136, Fleet-street. Agent for the American Edition, Mr. O. RICH, 12, Red Lion-square. Sold by G. W. M. RayNOLDS, Proprie or of the French, English, and American Library, 55, Rue Neuve, Saint Angustin, Paris.

CUNNINGHAM and SALMON, Printers,
Fleet-street.

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