The Sun revolves about its axis in about 251 sidereal days; Mercury, Venus, the Earth, and Mars, all revolve in about the same time, from 23P to 241h ; Jupiter and Saturn severally revolve in about 10b and 101h. 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 stars, it is only within the last twenty years that the distance of any etar from our system may be said to have been positively measured. [Patter, Lax or THE FIXED STARS.] 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 the 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 I 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 lllorroN. 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 continues 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 " haws of nature " are only expressions of the manner in which this preservation is seen to act, will look upon the "laws of creation" to be as simple and 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 past time, is the retort of semi-atheism against those who make it.
Many speculations 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, iu which it is 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, in Moo. Div] 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 charadter 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 oue of these things must be true ; either was what Mr. Whewell 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 of nature give to the solar system the constitution which we have described." Laplace then quotes Newton's Scholium [Psi:cetera, 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 is concerned, rather in approbation : "He repeats the same thought at the end of his Optics,' in which be 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 will again require its Author to pia 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 that the [unlimited] preservation of the Solar System is a part of the intentions of the Author of Nature I" 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 be 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 tho remark specially made on that sentence, has rather the appearance of being pointed at with approbation. With regard to the assertion that Laplace propounded the nebular theory as a primitire cause, it is true that he did so in his own sense of the words. Mr. WhoreII menus by primitive GIMSC a first cause, as those worth are usually understocal ; and he the question would have been much to the purpose if Laplace had really meant the RAMC thing as himself by the words primitire cause), "Was man, with his thought and feeling, his powers and hopes, his will and conscience, also produced as an ultimate result of the con densation of the solar atmosphere?" But Laplace speaks as follows: " Quelle est cette cause prize tire I J'exposerai our cells, clam Is note qui termine cello ouvrage, tine hypothese," &c. And in the very first words of this note we tied, " On a, pour remonter It la cause des mouvemens primitifs du sysame planetaire," &c. This then is what Laplace understood by primitire cause, a cause of the primitire motions ;—an improper use of language, if the reader pleases ; but when a man puts his own meaning on his own words, no one has a right to fix the consequences of another meaning upon him.