abstracts: spectroscopy 575 



MAGNETISM. — Terrestrial magnetism, United States magnetic tables 

 and charts for 1915. Daniel L. Hazard. U. S. Coast and Geo- 

 detic Survey. Spec. Publ. No. 44. 1918. 

 This publication contains the results of observations made in the 

 prosecution of the magnetic survey of the United States to the end of 

 1915, with corresponding values for January 1, 1915; the collected 

 results of observations at repeat stations used in determining the change 

 of the magnetic elements with lapse of time; the secular change tables 

 used in reducing the observed values to the common epoch January 1 , 

 1915; and five magnetic charts showing graphically the distribution of 

 the magnetic, declination, dip, horizontal intensity, vertical intensity 

 and total intensity in the United States on January 1, 1915. On the 

 declination, dip, and horizontal intensity charts there are also lines 

 showing the annual change of those elements in 1915. In addition to 

 the results obtained by the Coast and Geodetic Survey the collection 

 includes all available results of high grade from observations made by 

 others in the United States and adjacent land and water areas, includ- 

 ing those at stations in Mexico, Central and South America used in the 

 construction of the isogenic chart of the West Indies published in 1914. 



D. L. H. 



SPECTROSCOPY. — Wave lengths in the red and infra-red spectra of iron, 

 cobalt, and nickel arcs. W. F. Meggers and C. C. Kiess. Bur. 

 Stands. Sci. Paper No. 324. Pp. 15. 1918. 

 It has long been known that the sensitiveness of photographic plates 

 to yellow, red, and infra-red light may be increased by staining the 

 plates with certain dyes, but the use of such stained plates in spectrum 

 photography has not been very common. The long wave regions of 

 the arc spectra of ferrous metals were recorded on plates stained with 

 pinacyanol and with dicyanin. The photographs were made in the 

 first order spectrum of a concave grating with 645 cm. radius of curva- 

 ture. Exposures of ten minutes duration sufficed to register the spec- 

 trum up to 7000 A; between 7000 A and 9000 A, twenty to thirty min- 

 utes' exposure was sufficient; while five to ten hours of exposure recorded 



o , 



many lines whose wave-lengths exceed 10,000 A, or one micron. In the 

 arc spectrum of iron, 298 lines were measured between the wave-length 



o o o 



limits 6750 A and 10,689 A; 606 Imes w'ere measured between 5503 A 

 and 11,623 A in the arc spectrum of cobalt; and 290 lines between 5504 



o o 



A and 10,843 A in the arc spectrum of nickel. 



W. F. M. 



