130 



THE POPULAR SCIENCE MONTHLY. 



least ten per cent, of combustible matter. 

 It is known in the Western States as black 

 shale. Its precise geological horizon has 

 been a subject of debate. The conclusion 

 of the author is that " the Huron Shale of 

 Ohio is made up of the black shales of the 

 Lower Portage and Genesee." This depos- 

 it is an interesting one, from the fact that it 

 is the most important source of supply of 

 petroleum in this country, and also that 

 most of the gas-wells of Ohio and Pennsyl- 

 vania derive thence their supply of carbu- 

 retted hydrogen. 



If space permitted, we would be glad to 

 present the views of Professor Newberry 

 on the buried river channels — evidences of 

 glacial action — clay deposits of the Drift 

 age, and other subjects of interest to the 

 geologist. 



The reports of the local surveys by coun- 

 ties and districts are not only valuable to ge- 

 ologists, but are throughout of a thoroughly 

 practical character. These include thirty- 

 four counties of the State, besides reports 

 of the Hocking Valley coal-field. Perry, and 

 portions of Athens, and Hocking Counties, 

 and the Hanging Rock District. 



The reports of counties are illustrated 

 by maps and charts, of which there are twen- 

 ty, while fifty-three illustrations are printed 

 with the text. 



In the preface we are informed that Vol. 

 IV., Zoology and Botany, is now in the print- 

 er's hands, and that Vol. V., Economic Ge- 

 ology, is in progress. Besides these, full and 

 elaborate maps are in course of preparation. 



The work has been issued in editions of 

 20,000 copies — to the honor of Ohio, be it 

 said. 



Distribution of Heat in the Spectra of 

 Various Sources of Radiation. By 

 William W. Jaynes, Ph. D. Cambridge, 

 Mass. : University Press. Pp. 24. 

 This pamphlet is the thesis presented to 

 the Faculty of Johns Hopkins University 

 by the author upon applying for the degree 

 of Doctor of Philosophy. It first gives an 

 account of former experiments to determine 

 the distribution of heat in the spectrum ; 

 and then details the author's elaborate ex- 

 periments for the determination of the re- 

 sult. There is one plate of apparatus and 

 three large plates of the curves of thermal 

 intensity in different parts of the spectral 



region. He thus sums up the inquiry : " In 

 concluding this paper there is a strong 

 temptation to speculate upon the meaning 

 of the results obtained. That the geomet- 

 rical form of the curve should be so nearly 

 the same at all temperatures, and of the 

 same general form for all substances, is a 

 fact that probably must have an important 

 physical interpretation. Does not the simi- 

 larity of the curves for different substances 

 show a similarity of movement of the ulti- 

 mate components of the several substances, 

 and so point to a similarity of ultimate com- 

 position of all matter, the slight differences 

 in the grouping of these parts giving rise to 

 the comparatively slight variations from the 

 same form ? Certainly this is not proof, but 

 is it not evidence ? And is it not probable 

 that the superposition upon the radiations 

 from the ultimate atoms of the radiations 

 from the groupings of these atoms should 

 cause the curve, as a whole, to move slight- 

 ly to a shorter or longer wave-length, as the 

 weight of a group is lighter or heavier? 

 But I am aware that such speculations are 

 founded on too insufficient data, and I offer 

 these results merely as an experimental con- 

 tribution to the science of radiant energy." 



A Defense of Philosophic Doubt, being an 

 Essay on the Foundations of Belief. By 

 Arthur James Balfour, M. A., M. P. 

 Pp. 355. Price, $3.50. 

 The object of this book would not be 

 guessed from its title. It would be sup- 

 posed to imply an argument in favor of skep- 

 ticism, unbelief, or freethinking, in their 

 customary applications to religious belief. 

 But this is not the author's aim. On the 

 contrary, the work is " a piece of destruc- 

 tive criticism " directed against the founda- 

 tions of science. According to the author, 

 it is the function of philosophy to give an 

 account of the grounds of all belief and 

 disbelief, and he labors to show that all 

 the assumptions, principles, postulates, and 

 criteria of truth that are usually taken as 

 the basis of scientific knowledge are illusive 

 and indefensible. The independent exist- 

 ence of an external world is denied ; Kant, 

 Hamilton, Mill, and Spencer are refuted; 

 and the conclusion is reached that "science 

 is a system of belief which, for anything 

 we can allege to the contrary, is wholly 

 without proof. The inferences by which it 



