Geology and Mineralogy. 239 



9. On the Silver Voltameter and its use in determinations of 

 normal elements. — In a contribution from the Reichsanstalt, K. 

 Kahle discusses the subject and gives the results of a careful 

 inquiry of the electromotive force of a Clark and a Cadmium 

 cell, and a comparison with previously obtained results by means 

 of a Helmholtz electrodynamometer (Wied. Ann., lix, p. 532, 

 1896) of the electrochemical equivalent of silver. The final value 

 obtained is E = T1183 mg/sec. which is in accordance with the 

 previously obtained value. — Wied. A?m., No. 1, pp. 1-36, 1899. 



J. T. 



10. Absorption of light by a body placed in the magnetic field. — 

 Rhigi discusses the work of investigators who have occupied 

 themselves with the phenomena of absorption discovered by him. 

 It is shown that the Zeeman effect is accompanied by a rotation 

 of vibrations of which the wave lengths are close to those of the 

 radiations absorbed. According to Becquerel and Voigt, one 

 could predict this rotation from the facts of anomalous disper- 

 sion. Rhigi does not believe with MM. Corbino and Macaluso 

 that the rotation constitutes the principal cause of the appearance 

 of light in his experiments ; for the condition that the phenom- 

 ena of rotation may be observable, namely, great length of rays of 

 absorption, is not necessary and is even prejudicial. One cannot 

 maintain absolutely that Rhigi's experiments would lead to the 

 discovery of the Zeeman effect. They reveal the existence of a 

 phenomenon less simple — a Zeeman effect together with rota- 

 tions, more or less simple, of vibrations which, it may be, always 

 accompany it. — Comptes Refidus, No. 1, pp. 45-48, January, 1S99. 



J. T. 



II. Geology and Mineralogy. 



1. Recent Earth Movement in the Great Lakes Region ; by 

 Grove Karl Gilbert. (From the Eighteenth Annual Report 

 of the Survey, 1896-97. Part II.) — The question as to the exist- 

 ence at the present time of progressive changes of level between 

 the water and land in the region of the Great Lakes is one not 

 only of great theoretic interest, but also of much practical impor- 

 tance, since a relative rise of the water may have a profound 

 effect upon the value of property on the shores of the Lakes. 

 This subject is discussed by Mr. Gilbert with great care and 

 thoroughness. He remarks upon the earth movements which 

 characterized the closing epochs of the Pleistocene Period, as 

 clearly brought out by the studies of Dr. Spencer, Mr. F. P. Tay- 

 lor, and others, of the shore lines of the early glacial lakes that 

 covered more or less of the region. He quotes Dr. Spencer (1894) 

 as urging that this change of level has not ceased, and that it will 

 eventually turn the water of the Upper Lakes southward to the 

 Illinois and Mississippi Rivers, leaving the Niagara channel dry. 

 This is one consideration which has weight in the matter. 



Another is found in the condition of the estuaries which show 



