Page:Popular Science Monthly Volume 48.djvu/663

Rh phenomena, we pursue always and everywhere the same scientific method. We put like by the side of like, and seek what is common in diversity. In this way is the gradual mastery of the infinity of our phenomenal world achieved, and more effective means for compassing the purpose arise in successive development. From bare comparison we pass to system, from this to laws of Nature, and the most comprehensive form of these is compressed into the general principle. We perceive that the phenomena of the actual world, unlimited as is their diversity, still represent only quite definite and well-marked instances of formally conceivable possibilities. The significance of the laws of Nature consists in the determination of the real cases out of the possible, and the form to which they may all be traced back is the ascertaining of an invariant, a something which remains unalterable, even when all other criterions within the possible bounds defined by the law change. Thus we see that the historical development of scientific views is always associated with the discovery and elaboration of such invariants; in them are revealed the milestones of the highway of knowledge which mankind has trodden.

One such invariant of universal bearing is found in the idea of mass. This not only gives the constants of astronomical laws, but is not less invariably illustrated in the most incisive changes to which we can subject the objects of the outer world—chemical processes. For that reason this idea, as being highly adapted to the position, has been made the center of scientific legitimacy. It was, however, in itself too poor in substance to serve for the representation of the manifold phenomena, and had to be correspondingly extended. This was done by associating with that simple mechanical idea the series of properties, in their proportion, which are experimentally connected with the property of mass. Thus originated the idea of matter, in which was grouped all that was sensibly connected with mass, and continued with it, such as weight, volume, chemical properties, etc., and the physical law of the conservation of mass passed into the metaphysical axiom of the conservation of matter.

It is important to understand that with this extension a multitude of hypothetical elements were introduced into a conception that was in the beginning wholly free from hypotheses. Chemical processes, in particular, must be interpreted in the light of this view against the seeming, not as implying a disappearance of the matter affected by the change and its replacement by new matter with new properties. The theory rather became accepted that even when all the sensible properties of, for example, iron and oxygen disappear in iron oxide, iron and oxygen are nevertheless present in the resultant substance, and have only taken on other properties. We have now become so accustomed to this view