Page:Popular Science Monthly Volume 21.djvu/171

serve equally well to establish any other ratio, and who never thought of asking himself the question whether or not a diameter 1 and a circumference 318 were compatible—whether or not his postulates were consistent with each other—is closely analogous to the mental predicament of certain scientific specialists who are constantly multiplying forces, superable and insuperable, and all manner of entities with impossible or contradictory properties, for the purpose of explaining natural phenomena. When this is done with a proper insight into the nature and use of such fictions—with the understanding that they are mere devices for fixing ideas or colligating facts (to use Whewell's expression)—it is well enough. But, in many cases, the specialists have no such insight. They begin to treat the fictions here spoken of as undoubted realities, whose existence no one can question without subjecting himself to a Newcombian fnstigation. Take the case of the ether, the hypothetical substratum of luminar undulations. It is first mentioned simply as a fluid of the greatest tenuity, as wholly inappreciable to the senses, and as offering no resistance to atoms or celestial spheres. Thereupon, to meet the exigencies of the undulatory theory, it is endowed with a co-efficient of elasticity thousands of times greater than that of steel. Next, at the demand of some physicist or chemist, who wants to incase his atoms or molecules in ethereal atmospheres or envelopes, it is made as soft and mobile as hydrogen gas. First, it is looked upon as continuous; then, to explain the dispersion of light, it is made discontinuous, and "finite intervals" are interposed between its atoms. But now comes Clerk Maxwell, and shows that, if the constitution of the ether were atomic, consequences would ensue upsetting the whole theory of heat; or Helmholtz and Sir William Thomson, in order to be able to construct their vortex-atoms, require it to be absolutely frictionless and incompressible, and therefore continuous; and, accordingly, it is restored again to its ancient continuity, no matter what may become of Cauchy's theory of chromatic dispersion or Fresnel's theory of polarization. Originally there is but one ether; but presently Professor Norton contends that the luminiferous ether is not available for the purpose of explaining the phenomena of electricity and magnetism. He demands a second ether, filling the same space with the first; and his demand is complied with. In a short time Mr. Hudson appears with the claim that even the phenomena of light can not be accounted for on the supposition of a single light-bearing ether; and he must have two luminiferous media, "each possessed of equal and enormous self-repulsion or elasticity, and both existing in equal quantities throughout space, whose vibrations take place in perpendicular planes; the two media being mutually indifferent, neither attracting nor repelling"—and, again, his request is granted without further ceremony. To cap the climax, finally arrives the pangeometer, and insists that back of and behind all these ethers there is an independently real thing, an object of direct sensation,