Geology and Mineralogy. 155 



red lines are more widely separated than the components of the 

 doubled green lines, the effect being proportional to wave-length. 

 The most interesting line to try was the red cadmium line, since 

 this has been proved to be of specially simple constitution by 

 Michelson. We have recently been able to get the cadmium 

 spectrum well developed by means of a sort of spark arc between 

 the magnet poles, maintained by an induction coil excited by an 

 alternating machine; and we find that the magnetic doubling of 

 the chief lines occurs in precisely the same way with the spark 

 spectrum as with the flame spectrum, and that the red cadmium 

 line behaves in the same way as the others. The magnetic effect 

 is better seen, from a direction perpendicular to the line of force, 

 when a nicol is interposed in the path of the light, but rotation 

 of the nicol through 90° cuts it entirely off, accurately so when a 

 small spark is the source of light. — May 31.] 



II. Geology and Mlnekalogy. 



1. Recent publications of the IT. S. Geological Survey* — The 

 Seventeenth Annual Report for 1 895-96 has three parts, all issued. 

 Besides the paper already noted, Part I contains the following : 

 Magnetic Declination in the United States, by Henry Gannett, 

 pages 237, with map showing distribution of the magnetic decli- 

 nation in the United States in 1900. Further Contributions to 

 the Geology of the Sierra Nevada, by H. W. Turner, pages 241, 

 plates 30. Although much of this paper treats of structural 

 geology, the larger part is petrographical. Report on the Goal 

 and Lignite of Alaska, by W. H. Dall, pages 143, plates 11, with 

 an appendix on the fossil plants by F. H. Knowlton. Another 

 on the Paleozoic fossils by Charles Schuchert, and a third on the 

 Mesozoic fossils by Prof. A. Hyatt. G. F. Becker and Dr. Dall 

 were together on the Alaskan trip and Becker's report on the 

 gold of that country will appear in the Eighteenth Annual. The 

 Glacicd Brick Clays of Rhode Island and Southern Massachu- 

 setts, by N. S. Shaler, J. B. Woodworth, and C. F. Marbut, pages 

 51, plates 2. This paper supports the view that the glacial period 

 was divided into three great epochs of ice action separated from 

 one another by very long intervals. The Faunal Relations of the 

 Eocene and Upper Cretaceous on the Pacific Coast, by T. W. 

 Stanton, pages 56, plates 5. Notwithstanding their conform- 

 ability, Mr. Stanton recognizes a marked paleontological break 

 between the Upper Cretaceous and the Eocene of California and 

 Oregon. 



Part II of the Seventeenth Annual, Economic Geology and 

 Hydrography, contains the following papers: — The Gold Quartz 

 Veins of Nevada, City and Grass Valley, California, by W. 

 Lindgren, pages 249, plates 24. This paper, although chiefly eco- 

 nomic, contains much petrography. A folio of the region has 



* Issued since January, 1897. See list in this Journal for February, 1897, 

 page 153. 



