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THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. [Skptkmber, 



is to sav. from west to east. The planets and the satelhtes of which 

 the n oven enls of rotation can be observed equally turn on the.r con- 

 tres f on' west to east. In fine the rotary movement of the sun .s also 

 nffec d from west to east. There is therefore a total of forty- hree 

 ^novements similarly directed. By the calcnlat.ou of probab.lU.es 

 e e are more than four thousand milliards to one agamst th.s s.m.- 

 iude indirection of so ma.iy movements bei..g the eftect of chance 

 BufFon is, I believe, the first who has attempted to g.ve an account of 

 this singdaritv of our solar system. Wishi,.g to abstain fro™ re^o;'" 

 ine in the explanation of phi^nomena to causes out of nature, the cele- 

 l„!ted academician sought a physical origin or what .s coram<m ... 

 the movement of so many stars ; of so many stars, d.fferent in the.r 

 size, forms, and dista.ices, from the principal centre of attract.on. 

 This origin he thought he had found by making this tr.p e supposi- 

 tion; a fomet fell obliquely on the sun; it pushed before it a torrent 

 of fluid matter; this matter, transported according to its difierent de- 

 crees of levitv, more or less far from the sun, formed by concentration 

 all the know.", planets. The bold hypothesis of Button .s subject to 

 insurmountable clifficulties, I have already sufficiently >"»f;^^'"'.''^,3 

 in my .'otice on comets. I may therefore confine .nyself to point., g 

 out here in a few words the cosmogonic system which Laplace s.ib- 

 stituted for that of the illustrious author of the Natural History. 



Accordine to Laplace the sun was at a remote period, the central 

 nucleus of an immense nebulosity which had a very high temperature, 

 mid extended far beyond the region where Herschel now "O^s. At 

 that time no planet existed. The solar nebulos.ty was gifted w.th a 

 eeneral movement of revolution directed from west to east. On 

 cooline down it could not fail to sustain a gradual condensat.on, and 

 thenceforth to turn faster and faster if the nebulous matter extended 

 orgn'llyin the equatorial region as far as the l.mit at which he 

 cenuifu4l force esactlv counterbalanced the attract.v^ actioii of the 

 nucleus,°the molecules situated at that limit, should during the con- 

 dentation separate from the rest of the atmospher.c matter and form 

 an equatorial zone, a ring turning separately and with its pr..mt.ve 

 velocity. It may be conceived that analagous separations would tukt 

 place at diff-erent periods, that is to say, at various distances from the 

 nucleus, in the superior strata of the nebulos.ty, and that they would 

 Vh'e ri4 to a succession of distinct rings kept almost .n the same 

 Diane, and giltpd with diflerent velocities. This once adm.tted, we 

 easily see that the indefinite preservation of the rings would have re- 

 nuired in their whole circumference a composition l.ttle probable. 

 Each of them broke then in its turn into several masses whicliwere 

 endowed, as it is easily to be conceded, with a rotary movement in tlie 

 common direction of revolution, and which on account of their fluidity 

 assumed spheroidal forms. If we allow now that one of these sphe- 

 roids may have swallowed up all those arising from the same ri.ig, it 

 wiUbe sufficient to give it a mass superior to that of all the others. 

 In each of the planets in the vaporous state of which we have just 

 suoken, the mind recognizes a central nucleus g.-adually increasing .n 

 mass, and an atmosphere which presents at its successive l.mits, 

 phenomena entirely similar to those which the solar atmosphere, pro- 

 Ulv so called had presented to us. We thus assist at he birth of 

 t'he satellites and of the ring of Saturn. The system of which I have 

 iust eiven a sketch, has for its object to show how a nebulos.ty gilteU 

 with a general movement of rotation should in tln^ long run traiislorm 

 itself into a very luminous central nucleus (the sun), and into a series 

 of distinct spheroidal planets, distant one from another, all moving 

 around the central sun in the direction of the primitive movement ot 

 the nebulosity ; and how these planets would thus have arou.id their 

 centres movements of rotation similarly directed, how in fine the 

 satellites, when formed, could not fail to turn on themselves and 

 around the planets which carry them along, in the direction ol the 

 rotation of those planets, and of their circulating movement around 

 the sun We have just observed conformably with the principles ol 

 mechanics, the forces with which the particles of the nebulosity were 

 primitively sifted, in the movements of rotation and circulation ot the 

 distinct and compact to which these particles had given rise by ag- 

 elomeration. But in so doing we make only a single step. 1 '^ pri- 

 mitive movement of rotation in the nebulosity does not result from 

 simple attractions; this movement seems to indicate the action ol an 

 impulsive primordial force. Laplace is far from holding with respect 

 to this the almost general opinion of philosophers and mathematicians. 

 '' He does not believe that the mutual attraction of bodies primit.vely 

 motionless, would in the long run, reunite all these bodies in a state 

 of repose, around a common centre of gravity." He maintains on the 

 contrary, that three bodies without movement, of which two sUouia 

 be much larger in mass than the third, would not agglomerate into an 

 homogeneous mass, but only in exceptional cases. In general the two 

 larger bodies would unite together, while the third would revolve 

 around the common centre of gravity. Attraction would thus become 



the cause of a kind of motion to which impulse would seem alone 

 capable of giving birth. 



In might in truth be believed that in lay..ig down this part of h.s 

 system, Laplace had before his eyes the words which Jean Jacques 

 Rousseau had placed .n the mouth of the Savoyard curate, and which 

 he endeavoured to refute. "Newton has discovered the law of at- 

 traction," says the author of Emile, "but attraction alone would soon 

 reduce the universe to a motionless mass ; to this law it has been re- 

 quisite to add a projectile force to make the heavenly bodies describe 

 curves. Let Descartes tell us what physical law has made his vortices 

 turn round ; let Newton show to us the hand which directed the 

 planets on tangent of their orbits." . . 



According to the cosmogonic ideas of Laplace, comets, in the origin, 

 were not part of our system; they have not been formed at the ex- 

 pense of the matter of the immense solar nebulosity; they must be 

 considered as small wandering nebulosities which the attractive force 

 of the sun has deviated from their primitive path. Those of the 

 comets which penetrated into the great nebulosity at the period of its 

 condensation, and the formation of the planets, fell into the sun de- 

 scribing spirals, and would by their action, more or less, remove the 

 planes of the planetery orbits from the plane of the solar equator, with 

 which they would otherwise exactly have coincided. As to the 

 zodiacal light, that stumbling block on which so many theories have 

 fallen, it is composed of the most volatile particles of the primitive 

 nebulosity. These molecules not having combined with the equato- 

 rial zones, successively abandoned in the plane of the solar cq"^'"' 

 continue to revole at the distances at which they were primordially, 

 and with their original velocity. The existence of this extremely 

 rare matter, in the region occupied by the earth, and even only mthat 

 of Venus, seemed irreconcileable with the laws of mechanics ; but 

 that was when, by placing the zodiacal matter in the immediate de- 

 pendence of the solar photosphere, properly so called, there was im- 

 pressed on it an angular movement of rotation, equal to that ol this 

 photosphere, a movement by means of which its entire revolution 

 would only require twenty-five days and a half. 



Laplace presented "his conjectures on the formation of our solar 

 system, with the mistrust which everything must inspire which is not 

 the result of calculation and observation." Perhaps it is to be re- 

 gretted that they did not receive greater developement, particularly 

 in what regards the division of matter into distinct rings ; perhaps it 

 is unfortunate that the illustrious author has not sufficiently explained 

 ' himself as to the primitive physical condition, the molecular condition 

 of the nebulosity, at the expense of which were formed the sun, 

 planets, and satellites of our system ; perhaps it is to be regretted in 

 particular that Laplace should have thought proper to pass so slightly 

 over the possibility, evident according to him, of the movements of 

 revolution, resulting from the action of simple attractive forces, &c. 

 Notwithstanding these omissions, the ideas of the author of the Me- 

 canique Celeste are nevertheless the only ones which, by the.r 

 grandeur, coherence,, and mathematical character, can be truly con- 

 sidered as forming a physical cosmogony ; the only ones which in 

 the present day find a powerful support in the results of the recent 

 labours of astronomers on the nebulosities of every kind with which 

 the firmament is sprinkled. 



In this analysis we have thought proper to concentrate attention on 

 the Micanique C'ksle. The System of the World and the Analy- 

 tical Theory of Probabilities would not require less developeme.it 

 The Exposition of the System of the World is the Mkanique Celeste. 

 stripped of its grand panalopy of analytical formulas, through which, 

 must indispensably pass every astronomer who, according to the ex- 

 pression of Plato, wishes to know " what figures" govern the material 

 universe. It is in the Exposition of the System of the World that 

 persons unacquainted with mathematics must seek an exact a.id suHi- 

 cient idea of the methods to which physical astronomy owes its as- 

 tonishing progres. This work, written with noble simplicity, exqui- 

 site propriety of expression, and scrupulous correctness, concludes 

 with an abridgement of the history of astronomy, now classed, by an 

 unanimous judgment, among the finest monuments of the treneli 

 language. It 1ms often been regretted that Cesar, in his immortal 

 Commentaries, has confined himself to the relation of his own cam- 

 paigns; the astronomical commentaries of Laplace extend to ttie 

 orilin of society. The endeavours made in all ages to snatch from 

 the firmament new truths are there analysed with justice, clearness, 

 and profundity ; it is genius constituting itself the ..npartial appre- 

 ciator of genius. Laplace alway remained at the head of th.s grand 

 mission, and his work will be read with respect as long as the torch ol 

 science shall give forth light. .... »„ 



The calcuUTtion of probabilities, kept within proper l.mits, .nterests, 

 in an equal degree, the mathematician, the experimentE ists, and tne 

 statesman. From the period, already remote, when Pascal and Fermat 



