the third stratum, which has been found to resist infiltrations, that the substrata, to the depth of 86 feet, are of a nature that present no obstacle to the progress of a tunnel; we are informed that no water was met there. It is therefore through these substrata that it is proposed to penetrate, and to carry the line that is to cross the deep and navigable part of the river, leaving over the crown of the tunnel a head of earth of from 12 to 17 feet in thickness, quite undisturbed, (See Fig. 5). Admitting that, in descending to, or in ascending from, that line, we should come to a body of quicksand, such as that which was found within about 200 feet from the shore, it is then we should find in the combinations of the framing, before described, the means that are necessary for effecting, upon a large scale, what is practised, on a very small one, by miners when they meet with similar obstacles. Indeed, were it not for the means of security that are resorted to on many occasions, mines would inevitably be overwhelmed and lost. Although we may encounter obstacles that may retard the daily progress of the work, it is with satisfaction we contemplate that every step we take tends to the performance and ultimate completion of the object; and, if we consider that the body of the tunnel must exceed the length of Waterloo Bridge, it must be admitted that, if, instead of 2 years, 3 were necessary to complete the undertaking, it would still prove to be the most economical plan practicable for opening a land communication across a navigable river." In order to execute the tunnel beneath the Thames by the method described in the preceding paper, it is proposed to raise a capital of L. 160,000 by transferable shares of L. 100 each. The following are the heads of expence : ART. XIII. Observations on the Effects of Heat and of Motion. In a Letter to J. F. W. HERSCHEL, Esq. F. R. S. Lond. and Edin. from M. SEGUIN. Communicated by Mr HERSCHEL *. I ANNONAY, 12th Sept. 1822, HAVE taken the liberty of submitting, through your means, to the learned Society of which you are Secretary, a new method of considering the effects of heat and of motion, which my granduncle M. Montgolfier, with whom I spent a great part of my youth, had often discussed with me. The principle which he maintained was, that the vis viva could neither be created nor annihilated, and consequently, that the quantity of motion on the earth had a real and finite exist ence... In order to obtain an explanation of this result, I have observed, that, as all known bodies are elastic, and susceptible of experiencing variations of volume, the limits of which are unknown, their molecules must necessarily be at a distance from each other. As even the most solid and dense bodies are capable of being evaporated, a property which is indicated by their smell, we may conclude, that there escapes from them at each instant an infinity of molecules, which, from their tenuity, elude all the means of comparison which we can employ. In order to assign to them the condition either of a solid, a liquid, or a gas, it is necessary to suppose the existence, and the combination of two forces, which are sometimes in equilibrio, and sometimes predominate the one over the other. We shall admit, then, the supposition, that these two forces may be the same as those which regulate our planetary system, and that the molecules of bodies are subject to circulate round one another, so • This ingenious paper was communicated by its author to J. F, W. Herschel, Esq. as Secretary to the Astronomical Society of London; but being on a subject not Astronomical, Mr Herschel was so kind as to transmit it to Dr Brewster, for insertion in this Journal, that each body, though it appears at rest, has really a certain quantity of motion, whose measure will be a function of the mass, and the velocity of the molecules in motion. Upon these suppositions, it is obvious, that, during the im pact of two bodies, all the quantity of motion which is not employed in giving the body which is struck a motion of transla tion, will go to augment the quantity of interior motion which it possesses; and if this motion takes place in circles or ellipses, the parts will recede from the centre of attraction, and the body will increase in volume. In this state it will have a tendency to transmit the excess of motion which it possesses, to bodies which are near it, or to parts which it will emit in greater number, in following the same law. If the quantity of motion is so great, that the attraction of the molecules can no longer be in equilibrio with their angular velocities, the body will remain in the gaseous state, till it has transmitted to other bodies the excess of velocity which it pos sesses. The particles, in continuing to circulate at a distance, or in detaching themselves from bodies with different velocities, may make different impressions upon organised bodies, viz. that of light, if the velocity is sufficiently great to make it traverse the humours of the eye; that of heat or flame, if their number is sufficiently great to put in motion or evaporate the organised parts, and that of both heat and flame, in the two cases united. Bodies, in short, being subject to circulate in circles or in ellipses, ought to group themselves together, according to the simplest law of solids, inscribed in these two figures. It is not difficult to observe the connexion which this theory has with magnetic phenomena, as well as the objections which may be made to it; but I shall forbear entering into more ample details, lest I should abuse the patience of the Society, if it should deign to notice an inquiry, which has for twenty years been the subject of my reflexions, assisted by those of the disciples of M. Montgolfier, who, like me, have had the advantage of living near him. I shall now conclude, by pointing out the application of this new theory to four facts, selected from the crowd of those which it may serve to explain, The first is the quantity of motion which is suddenly developed by a glass tear (Prince Rupert's Drops), which has been dropped red-hot into water, when the slightest derangement has taken place in some of its parts. The second relates to the effect of the steam-engine; for, if we consider the cause of it to be the caloric, it is not easy to see why we could not produce an indefinite number of oscillations with the quantity of caloric necessary to produce the first, if we could by any means whatever employ the low temperatures which are lost, to renew the effect. Whilst, if, as we suppose, an angular motion has been changed into a rectilineal motion, or into a motion of translation, we should find, after the effect, only the quantity of motion, or the caloric, which has not been employed in producing the useful effect. The third fact consists in giving a satisfactory explanation of the great cold which exists in the higher regions of our atmosphere, whose temperature on the contrary, ought to be more elevated, by the quantity of caloric abandoned by condensed vapours, and the warmest gases, which tend upwards, by their extreme levity. If we apply our theory to this case, we shall observe, that a gaseous body, on escaping at a tangent, in a direction contrary to that of its gravitation, is subject to the same laws as all other bodies in similar circumstances; and that, consequently, when it has arrived at the limit indicated by its initial velocity, it is found at rest, or, in other words, deprived of its caloric, and obliged to absorb a new quantity from surrounding bodies, in order to be reconstituted with the quantity necessary to de termine its existence in any state whatever. The fourth fact relates to the motion produced by organised bodies, and may be explained in the same manner as the steamengine, which appears to me, in a great state of simplicity, to resemble, in a high degree, the vital functions, enjoying, like them, motion and heat, while it is furnished with oxygen and fuel. If you consider these views, on a subject of vast extent, as meriting to be submitted to the distinguished members of your Society, I do not doubt, that, when viewed in the aspect in which I have been able to place them, they will not be able to 2 |