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THE POPULAR SCIENCE MONTHLY.

"The various attacks on the theory of descent," says President Jordan, "have nearly all centered on the question of the origin of man." But these attacks are wholly unreasonable. "Our objections to recognizing our kinship with the lower forms—if we have any such objections—rest on reasons outside the domain of knowledge. They do not rest on religious grounds. . . . Looking over the history of human thought, we see the attempt to fasten to Christianity each decaying belief in science. That the earth is round, that it moves about the sun, that it is old, that granite ever was melted—all these beliefs, now part of our common knowledge, have been declared contrary to religion; and Christian men who knew these things to be true have suffered all manner of evil for their sake." A short sketch of the life of Darwin is prefixed to the essay.

Researches on Diamagnetism and Magne-Crystallic Action. By John Tyndall D. C. L., LL. D., F. R. S. New York: D. Appleton & Co. Pp. 288. Price, $1.50.

The researches embodied in this volume cover the first six years of Prof. Tyndall's experimental work. The first investigation of the series treats of the deportment of crystals, and of other bodies possessing a definite structure, in the magnetic field. Plücker had discovered that deportment, and had attempted to account for it by supposing new forces and new laws. Faraday followed and corroborated Plücker, and added one more hypothetical force. These forces were held to be wholly distinct from magnetism and diamagnetism. Tyndall and Knoblauch found a much simpler way of accounting for the phenomena observed, which, in place of the assumption of three new forces, required only a simple modification of known forces, to which they gave the name elective polarity. Prof. Tyndall's first investigation on the subject of diamagnetic polarity is described in the "Third Memoir" of this volume. Supplied with more adequate apparatus and material, he prosecuted the research as recorded in the "Fourth Memoir," subjecting the deportment of diamagnetic bodies to an exhaustive comparison with that of magnetic bodies, which showed that the diamagnetic force had the same claim to be called a polar force as the magnetic. In the "Fifth Memoir" are described experiments made with a very delicate apparatus, which proved that the theory of diamagnetic polarity would stand the severest tests. The application of the doctrine of polarity to magne-crystallic phenomena is the subject of the "Sixth Memoir." Appended to these papers are letters by Weber, Faraday, and Tyndall, relating to the investigations, together with some brief descriptions of apparatus.

Journal of Morphology. Vol. II, No. 1. Boston: Ginn & Co. Pp. 190.

This number of the "Journal" contains five papers. The first is a brief account of "Observations on the Structure of the Gustatory Organs of the Bat (Vespertilio subulatus)," by Frederick Tuckerman, M. D. This is followed by a paper by Prof. E. D. Cope, "On the Tritubercular Molar in Human Dentition." Prof. Cope has investigated the variation in the number of tubercles forming the crown of the superior true molars in man, and has concluded that "the quadritubercular type of molar crown, illustrated by the first superior true molar of man, belongs to the primitive form from which all the crest-crowned (lophodont) molars of the hoofed placental mammals have been derived; and second, this quadritubercular type of molar has itself been derived from a still earlier tritubercular crown by the addition of a cusp at the posterior internal part of it." He says, further, that "the tritubercular superior molars of man constitute a reversion to the dentition of the Lemuridæ of the Eocene period of the family of Anaptomorphidæ; and, second, that this reversion is principally seen among the Eskimos, and the Slavic, French, and American branches of the European race." In the lowest existing races the quadritubercular type predominates, while the neolithic dentitions examined are of an intermediate character, thus showing a superior position to these races. The third paper is by C. O. Whitman, on "The Seat of Formative and Regenerative Energy," and deals with the question whether the cytoplasm is a passive body, moving only as it is acted upon by external forces and influences emanating from the nucleus, or whether it has powers of its own which make it capable also of au-