C81 



SOLAR SYSTEM. 



SOLAR SYSTEM. 



002 



found when they rise through the ecliptic from the southern to the 

 northern side of it. On the inner circle are represented the longitudes 

 of their perihelia, or points of nearest approach to the Sun. The slow 

 changes which take place in these elements are noted in the articles 

 devoted to the different planets. 



A general view of the elements of the minor planets has already 

 been given. [ASTEROIDS.] 



Jupiter and his satellites might be inclosed in a sphere having a 

 radius of about 24 times as great as that of the Sun ; Saturn and his 

 satellites in a sphere of 7} the radius of the Sun; Uranus and his 

 satellites in a sphere of 44 the radius of the Sun; and Neptune and 

 his satellite in a sphere of which the radius is a little greater than the 

 Sun's radius. The Earth and Moon [M-oos] might be contained in a 

 sphere of one-half the radius of the Sun. 



In apparent diameter Mercury varies from 5" to 12"; Venus from 

 10" to 61"; Mare from 4" to 18"; the small planets have diameters 

 hardly measurable ; Jupiter from 30" to 46" ; Saturn from 14" to 18"; 

 Uranus from a little less to a little greater than 4" ; Neptune oscillates 

 about 3". . 



If the radius of the Sun were divided into 1000 parts, there would 

 be as follows in the radii of the several planets: Mercury, 34; Venus, 

 8| ; the Earth, 9 ; Mars, 4 ; Jupiter, S74 ; Saturn, 85 ; and Uranus, 

 39. If the bulk of the Sun were divided iutd a million of parts, 

 Mercury would be a little less than one-twentieth of one of the parts ; 

 Venus, two-thirds of a part ; the Earth, three-quarters of a part; Mara, 

 one-tenth of a part ; Jupiter, 925 parts; Saturn, 720 parts; Uranus, 

 58 parts ; Neptune, 120 parts. The Moon is about the third part of 

 Mercury in bulk. 



The masses of the planets vary very much from what they would be 

 if they were nearly of the same substance. From the effects of the 

 planets in attracting their satellites, compared with the effects of the 

 Sun upon themselves, it is found that if, according to Cavendish's 

 experiment, we take the Earth to be, at a mean, 54 times the density 

 of water, or about half that of lead, the Sun may be considered, as to 

 density, to be made of asphalt urn, or rather heavy coal ; Jupiter, of 

 the same ; Uranus and Neptune, each of a material very little heavier ; 

 Saturn, of maple- wood ; the Moon, of diamond or topaz. By other 

 modes, of course, than that of their satellites, Mercury is found to be 

 three time* as dense as the Earth ; Venus, of about the same density ; 

 and Mars, about three-quarters as dense as the Earth. 



The Sun revolves about its axis in about 254 sidereal days; Mercury, 

 Venus, the Earth, and Mars, all revolve in about the same time, from 

 234 h to 244 k ; Jupiter and Saturn severally revolve in about 10 h and 

 104 k . About Uranus and Neptune, nothing is known in this respect. 



From what precedes, a sufficient general notion may be collected of 

 the dimensions of the Solar System, and we now proceed to some other 

 points connected with it. As to its place among the fixed stare, it is 

 only within the last twenty years that the distance of any star from 

 our system may be said to have been positively measured. [PARAL- 

 LAX OF THE FIXED STABS.] The star 61 Cygni is shown to be more 

 than 340,000 times as far from our system as its most distant dis- 

 covered planet is from the Sun. As to the question of the motion of 

 tin- Solar System in space, consult the article which follows. 



The next question may be, is there any evidence in our System of 

 any secondary law of formation, indicating a connection between the 

 mode of creation of one planet and another ? The will and power of 

 the Creator are the final causes both of the initiation and maintenance 

 of this vast machine ; but in the latter there are visible secondary 

 laws, that of attraction, for instance : were there any in the former ? 

 Attempts at investigation on this point have been frequently considered 

 atheistical ; a foolish notion, arising out of those views to which we 

 have alluded in MOTION. Those who can only think of the Creator 

 and forget the Maintainer, and who virtually separate the office of the 

 latter, and give it to the " laws of nature," may reasonably fear that 

 they would have to give up also the former office to the " laws of 

 creation," if such were found ; which would be (but owing only to 

 their own interpretation ,of the manner in which the world continue* to 

 exist) a renunciation of the idea of Deity in the contemplation of the 

 manner in which it began to exist. But to those who keep constantly 

 in view the fact which no modern theist disputes, that the same power 

 which created continues to create in preserving, and that the " laws of 

 nature " are only expressions of the manner in which this preservation 

 is wen to act, will look upon the " laws of creation " to be as simple 

 ami natural an object of philosophical inquiry as those of the ascent 

 of sap in a plant, or of the revolution of a planet. The proper reply 

 to a charge of atheism brought against those who investigate any mode 

 of action of the Creator of the universe, at any pant time, is the retort 

 of semi-atheism against those who make it. 



Many speculation!) have been made upon the formation of the several 

 planets, but none which has any appearance of connecting the phe- 

 nomena of one planet with those of another, except by Laplace (' Sys- 

 teme du Monde,' vol. ii., note 7), in what has been called the nebular 

 hypothesis. This conjectural theory, which is well worthy of atten- 

 tion, never received any particular notice, to our knowledge, from any 

 writer in this country, until Mr. Whewell's ' Astronomy and General 

 Physics,' the third of the Bridgewater Treatises, appeared, in which it 

 in announced that the nebular theory was ushered in with expressions 

 which showed Laplace to be a professor of atheism. What Laplace 



really thought on these subjects.as we have said before [LAPLACE,inBioo. 

 Div.J we do not know, nor would it really matter if he were what he was 

 represented to have been ; for a conjecture may be ingenious, and a 

 theory sound in its details, even though its author made it stand in 

 the place of a Creator. But considering the collateral associations 

 connected with such a charge, it will be well to examine into the fact 

 whether there was any such announcement ; and to do this fairly, we 

 must quote both Mr. Whewell and Laplace. The former says, " We 

 have referred to Laplace as a profound mathematician, who has strongly 

 expressed the opinion that the arrangement by which the stability of 

 the Solar System is secured is not the work of chance ; that ' a primi- 

 tive cause has directed the planetary motions.' This author, however, 

 having arrived, as we have done, at this conviction, does not draw from 

 it the conclusion which has appeared to us so irresistible, that ' the 

 admirable arrangement of the Solar System cannot but be the work of 

 an intelligent and most powerful Being.' He quotes these expressions, 

 which are those of Newton, and points at them as instances where that 

 great philosopher had deviated from the method of true philosophy. 

 He himself proposes an hypothesis concerning the nature of the primi- 

 tive cause, of which he conceives the existence to be thus probable." 



Here are two assertions : 1. That it is the doctrine of an intelligent 

 Creator which Laplace " points at " as a deviation from true philosophy; 

 2. That Laplace proposes his nebular hypothesis as a primitive cause. 

 We pay a writer of Mr. Whewell's character the compliment of insert- 

 ing here matter which would more appropriately appear in a review of 

 his work : and we deny that Laplace has been well described in either 

 assertion. Our object is to clear the nebular hypothesis from the 

 unphilosophical character with which its first appearance is thus pre- 

 sented, and by no means to uphold the moral dignity of Laplace. 

 Until the biting facts connected with his treatment of his benefactor 

 are answered or explained, that great mathematician must be called a 

 time-server ; and we suspect that his ' Systeme du Monde ' only treats 

 the intelligent Creator whom his mind acknowledged in the same 

 manner as he afterwards treated Napoleon. It was published in 1796, 

 a period which would well explain the mere suppression of all allusion to 

 the Supreme Being : and one of these tilings must be true ; either 

 'Laplace was what Mr. \\~hewell styles him, or he had not the courage 

 to declare himself otherwise in his age and country. But what we 

 have here to do with is the assertion that he did more that he 

 attacked the doctrine of a Supreme Being. His words are as follows, 

 the passages to which we wish to draw attention being in Italics : " I 

 cannot here help observing how much Newton has departed on this 

 point from the method which he elsewhere so happily applied. After 

 the publication of his discoveries, this great geometer, abandoning him- 

 self to speculations of another nature, inquired into the motives which 

 made the Author <>f nature give to the solar system the constitution 

 which we have described." Laplace then quotes Newton's Scholium 

 [PnraciPlA, cols. 742-743, where we have translated the whole] thus : 

 " And all these regular motions hare no origin in mechanical causes,"* 

 &c., &c., down to "all parts of the heavens." He then further quotes, 

 " This most elegant group, &c., can only arise from the design and 

 government of a powerful and intelligent Being." He (Laplace) con- 

 tinues thus, speaking, so far as the mere notion of a Supreme Being ia 

 concerned, rather in approbation : " He repeats the same thought at 

 the end of his ' Optics," in which he would have been still more con- 

 firmed if he had known what I have demonstrated, namely, that the 

 arrangement of the planets and satellites is precisely that which makes 

 a certain provision for their stability. ' Blind destiny,' says Newton, 

 ' can never make the planets move thus with such small irregularities, 

 which appear to come from the mutual action of the planets and 

 comets, and which will probably become greater and greater in the course 

 of time, until at last the system wiU ayain require its Author to put it in 

 order.' But," proceeds Laplace, " may not this arrangement of the 

 planets be itself a consequence of the laws of motion ? and may not the 

 Supreme Intelligence, which Newton makes to interfere, have already 

 made it depend upon a more general law ? Are we to affirm tluit t/te 

 [unlimited] preservation of the Solar System is a part of the intentions 

 of the Author ofXature!" This we should sum up as follows: 

 Laplace charges Newton with a departure from philosophical prin- 

 ciples in 1, speculating on the motives of the Creator ; t 2, assuming 

 the probability that his works would not last his time without his own 

 supernatural interference; 3, assuming that he intended to preserve 

 the Solar System for ever. But Mr. Whewell singles out only one part 

 of Laplace's quotation, and, without paying any attention to the 

 remarks which explain his meaning, declares that Laplace " pointed at " 

 Newton's declaration of belief in God as a piece of bad philosophy ; 

 whereas this part of his quotation is only followed by the remark how 

 much stronger he himself (Laplace) had been able to make the sort of 

 evidence on which Newton rested ; and the sentence selected by Mr. 

 Whewell as " pointed at," coupled with the remark specially made on 

 that sentence, has rather the appearance of being pointed at with 

 approbation. With regard to the assertion that Laplace propounded 



* Laplace evidently thought that by mechanical causes Newton meant what 

 we now call second causes. See the reference just made. 



f Newton's Scholium does not seem to us to do any such thing ; but that is 

 not tlie question. Laplace's approval or disapproval is of course to be applied 

 to his own interpretation of Newton's moaning, not to ours. 



