Geology and Natural History. TT 



cadmium sulphate and cadmium amalgam in the proportions 

 employed in the cells used at the Reichsanstalt, are not well 

 founded, at least when the thirteen and twelve per cent amalgam 

 is employed. — Ann. der Physik 9 No. 5, pp. 1-50. j. t. 



11. Electrical Flow in Gases. — L. Stark gives a theoretical 

 discussion of this subject in which he shows under what condi- 

 tions Ohm's law does not apply to electrical discharges in Plucker 

 tables. The streaming and the phenomena of stratification 

 depend upon the rate of arrival and departure of ions — also upon 

 the amount of ionization and mobilization. Ohm's law holds for 

 that portion of the discharge in which the ionization remains con- 

 stant. In general there are only portions where this is true. In 

 the neighborhood of the electrodes on account of the transport of 

 free ions by the streaming the ionization is lowered. This happens 

 especially at the cathode. In metallic conductors the force lines 

 coincide with the stream lines. This is not true in the case of 

 electrical discharges in gases. The author discusses also the 

 inner electromotive force developed in electrical discharges. He 

 also takes issue with Professor J. J. Thomson theory of stratifica- 

 tion. — Ann. der Physik, pp. 89-112, No. 5, 1901. j. t. 



12. A Treatise on Electro-Magnetic Phenomena and on the 

 Compass and its Deviations aboard Ship ; mathematical, theoreti- 

 cal, and practical ; by Commander T. A. Lyons, U. S. Navy. 

 Volume I, pp. xv and 556. New York, 1901 (John Wiley & 

 Sons). — The author has undertaken the preparation of an 

 exhaustive treatise upon the use of the magnetic needle on ship- 

 board. This is a subject of the greatest importance as well as of 

 very general interest, and one which it is difficult to find ade- 

 quately treated in any single volume. We have before us the 

 discussion of the physical subjects which form the basis of the 

 practical discussion which is to follow. In order to bring out 

 clearly the nature of- the periodic changes that take place in the 

 earth's magnetism, as well as the complex relations of magnetism 

 and electricity in general to the ether, the author has begun with 

 the foundation subjects and treats them in a familiar and popular 

 way, so as to be intelligible to one whose studies have not been 

 definitely along this line. For example, he treats of wave motion 

 generally, from the sound wave to those of Hertz, and in the 

 part of the volume following, discusses not only the magnetism 

 of the earth, and the methods of determining magnetic elements, 

 but also the phenomena of magnets and magnetic fields in general. 

 The second volume, which is to contain the discussion proper, 

 will be awaited with interest. 



II. Geology and Natural History. 



1. The Eocene Deposits of Maryland, by William Bullock 

 Clark and George Curtis Martin, pp. 1-92; and Systematic 

 Paleontology, by Messrs. Case, Eastman, Ulrich, Clark, Martin, 

 Vaughan, Bagg, Hollick. Pp. 93-331, Plates l-lxiv. Mary- 



