660 THE POPULAR SCIENCE MONTHLY. 



fill objects we are gazing at works in process of formation as they lie 

 plastic under the creative hand of the Almighty. Nor is it possible 

 to withhold the inference thus probably was the world we live in, 

 and the solar system of which we form a part, evolved out of chaos. 



The labors of Laplace commenced where Herschel ended. Herschel 

 described what he saw. Laplace showed by mathematics how the 

 known laws of gravitation could form, and probably did form, from 

 such partially-condensed mass of matter an entire planetary system. 



It is supposed that a film of vaporous matter filled up the space 

 which is now bounded by the orbit of the outermost planet of our sys- 

 tem. To the eye of an observer, if such there were, in a distant star 

 such a vapor would appear like one of the numerous nebulae which are 

 everywhere visible in the heavens. 



Laplace supposed that this nebula, extending beyond what is now 

 the orbit of Neptune, possessed a rotatory motion round its centre of 

 gravity, and that the parts of it which were situated at the limits 

 where the centrifugal force exactly counterbalanced the attractive 

 force of the central nucleus were abandoned by the central mass. 

 Thus, as the nucleus became more and more dense under the action 

 of gravity, were formed a succession of rings concentric with and 

 revolving round the centre of gravity. Each ring would break up 

 into masses which would be endued with motions of rotation, and 

 would in consequence assume a spheroidal form. These masses 

 formed the various planets, which, in their turn condensing, cast off in 

 some instances their outlying rings, as the central mass had done, 

 and thus formed the moons or satellites which accompany the planets. 

 As each planet was in turn cast off, the central mass contracted itself 

 within the orbit of that last formed, till, after casting off Mercury, 

 it gathered with immense energy round its own centre and formed 

 the sun. 



Laplace's mechanical explanation does not rest only on theory. It 

 has been experimentally shown that matter under certain conditions 

 would exhibit phenomena similar in many important particulars to 

 those which Laplace was led by mathematical considerations to sup- 

 pose. Prof. Plateau, several years ago, tried the experiment of pour- 

 ing olive-oil into alcohol and water, mixed in such proportions as ex- 

 actly to equal the density of the oil. The oil thus became a liquid 

 mass relieved from the operation of gravity, and free to take any 

 exterior form which might be imposed by such forces as might be 

 brought to bear upon it. The oil instantly took the form of a globe 

 by virtue of molecular attraction. Prof. Plateau then introduced a 

 wire into the globe of oil in such a manner as to form for it a vertical 

 axis. The wire had on it a little disk coincident with the centre of 

 the globular mass, and by turning the axis the oil was made to re- 

 volve. The sphere soon flattened at the poles and bulged out at the 

 equator, thus producing on a small scale an effect which is admitted 



