BLTC Press Titles


available for Kindle at Amazon.com


The Characters of Theophrastus

Theophrastus


Through the Looking Glass

Lewis Carroll


Leaves of Grass

Walt Whitman


The Souls of Black Folk

W. E. B. DuBois


Explanations

by Robert Chambers

Excerpt:

A little after the stoppage of the rotatory motion of the disc, the ring of oil, losing its own motion, gathers once more into a sphere. If, however, a smaller disc be used, and its rotation continued after the separation of the ring, rotatory motion and centrifugal force will be generated in the alcoholic fluid, and the oil ring, thus prevented from returning into the globular form, divides itself into "several isolated masses, each of which immediately takes the globular form." These are " almost always seen to assume, at the instant of their formation, a movement of rotation upon themselves—a movement which constantly takes place in the same direction as that of the ring. Moreover, as the ring, at the instant of its rupture, had still a remainder of velocity, the spheres to which it has given birth tend to fly off" at a tangent; but as, on the other side, the disc, turning in the alcoholic liquor, has impressed on this a movement of rotation, the spheres are especially carried along by this last movement, and revolve for some time round the disc. Those which revolve at the same time upon themselves, consequently, then present the curious spectacle of planets revolving at the same time on themselves and in their orbits. Finally, another very curious effect is also manifested in these circumstances: besides three or four large spheres into which the ring revolves itself, there are almost always produced one or two very small ones, which may thus be compared to satellites. The experiment which we have thus described presents, as we see, an image in miniature of the formation of the planets, according to the hypothesis of Laplace, by the rupture of the cosmical rings attributable to the condensation of the solar atmosphere."*

Such illustrations certainly tend to take from the nebular cosmogony the character of a "splendid vision," which one of my critics has applied to it. I may here also remind the reader that there are other grounds for this hypothesis, besides observations on the nebulae. Overlooking the zodiacal light, which has been thought a residuum of the nebulous fluid of our system, we find geology taking us back towards a state of our globe which cannot otherwise be explained. It was clearly at one time in a state of igneous fluidity,—the state in which its oblately spheroidal form was assumed under the law of centrifugal force. Since then it has cooled, at least in the exterior crust. We thus have it passing through a chemical process attended by diminishing heat. Whence the heat at first, if not from the causes indicated in the nebular

* Dr. Plateau on the Phenomena presented by a free Liquid Mass withdrawn from the action of gravity. Taylor's Scientific Memoirs. November, 1844.

hypothesis? But this is not all. In looking back along the steps of such a process, we have no limit imposed. There is nothing to call for our stopping till we reach one of those extreme temperatures which would vaporize the solid materials; and this gives us exactly that condition of things which is implied by the nebular cosmogony.

Of particular objections it is not necessary to say much. That there should be difficulties attending such a hypothesis is only to be expected; but where general evidence is so strong, we should certainly be scrupulous about allowing them too much weight. It is represented, for instance, that the matter of the solar system could not, in any conceivable gaseous form, fill the space comprehended by the orbit of Uranus. If this be the case, let it be allowed as a difficulty. It is pointed out that the planets do not increase regularly in density from the outermost to the innermost. Their sizes are also not in a regular pro"gression, though the largest, generally speaking, are towards the exterior of the system. It was not, perhaps, to be expected, that such gradations should be observed; but, grant there was some reason to look for them, their absence constitutes only another and a slight difficulty. Then we know no law to determine the particular "stages at which rings are formed and detached." Be it so— although something of the kind there doubtless is, as the distances of the planets, according to Bode's law, observe a geometrical series of which the ratio of increase is 2. From these objections, which cannot now be answered, let us pass to some which can.

It has been said that a confluence of atoms towards a central point, as presumed by the nebular hypothesis, I

would result, not in a rotation, but in a state of rest.* According to the North British Review—" . . . Supposing the uniformly distributed atoms to agglomerate round their ringleader, the space left blank by the slow advance of the atoms in radial lines converging to the nucleus, must be a ring bounded by concentric circles, the outermost circle being the limit of the nebulous matter not drawn to the centre of the nascent sun. Now, as all the forces which act upon the agglomerating particles, whether they proceed from the circumference of the undisturbed nebulous matter, or from the gradually increasing nucleus, must have their resultants in the radial lines above mentioned, —there can be no cause whatever capable of giving a rotatory motion to the mass. It must remain at rest."


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