It is frequently said that the days of the discovery of general principles and far-reaching laws are past, and that students of science are now settling down to minor questions and the elaboration of details. The amount of specialized work, unproductive of immediate result in general truths, is naturally increasing, both because of the assiduity of scientific workers and because each general truth brings a number of minor problems. But the acquisition of wide theories is by no means at an end when we are told, as we have been during the last year, that the nebular hypothesis of Laplace is at variance with the facts; that the atoms are made up of smaller bodies whose nature can be known; that inertia and gravitation are not special facts by themselves, but are the results of the electrical charges of bodies. In papers in the Journal of Geology and the Astrophysical Journal, Prof. T. C. Chamberlin and Dr. F. R. Moulton seek to show that the nature of the earth's atmosphere is not compatible with the traditional idea of the formation of the earth from a hot gaseous ring; that the force of gravity would not cause such a ring to form a sphere; that the matter given off by a rotating spheroid of gas would not go off in the form of rings, and that the present mechanical arrangement of the solar system could not be derived from a spheroidal nebula such as Laplace assumed. It is suggested that the spiral nebulæ may offer conditions analogous to those of our own solar system in its early stages. The hypothesis receives confirmation from the important paper published just before his death by Keeler, and described by Professor Campbell in the obituary notice published above. Keeler's beautiful photographs with the Crossley reflector, several of which are reproduced by Professor Newcomb in the opening article of this issue of the Monthly, indicate that most nebulae are in fact spiral.
Recent researches in molecular physics threaten to disqualify the time honored position of the atoms as the smallest known particles of matter and to push the analysis of material substances to a point where the dreams of a primary order of sub-atoms or corpuscles whose varying combinations shall account for the so-called 'elements' seems almost probable. The work of Prof. J. J. Thomson and others on the electrical condition of gases has resulted in the hypothesis that the ions or bodies carrying the electric charges are not greater than one-thousandth the mass of the hydrogen atom; further, that the mass of each ion is the same in the case of all the gases tried, regardless of their atomic weights. The latter statement indicates that atoms of totally different constitution yet consist of corpuscles that are alike at least in mass. Although the experiments and reasoning which have led to these conclusions are beyond the comprehension of any but the specialist, and so cannot be suitably given in this connection, it should be remembered that the conclusions are far from being mere speculations. On the contrary, they are the result of the most careful experimental work, accord well with a number of facts and have already been tentatively applied to the explanation of other phenomena. Thus, Dr. Reginald A. Fessenden has arrived at certain far reaching hypotheses concerning the possible explanation of inertia and gravitation in terms of electric charges. In a recent issue of Science he writes: "We thus find that both inertia and gravita-
