562 abstracts: geology 



The metals are all of American manufacture and are probably of 

 as high a degree of purity as has been attained in the preparation of 

 relatively large amounts of such materials. The chemical analyses 

 show purity as follows: zinc, 99.993 per cent; tin, 99.988 per cent; 

 copper, 99.987 per cent; aluminium, 99.68 per cent. B. S. 



MAGNETISM. — An experimental study of the Fahy permeameter. 

 Charles W. Burrows and Raymond L. Sanford. Bureau of 

 Standards Scientific Paper No. 206 (Bull. Bur. Stds., 14: 91-159). 

 1917. 

 This permeameter was developed during the course of an investiga- 

 tion at the Bureau of Standards of the magnetic-mechanical properties 

 of steel. In order to ascertain the degree of accuracy attained, as well 

 as its fitness for general laboratory use, a critical experimental study 

 of the instrument in its present form has been made. The instrument 

 represents a distinct advance in the measurement of the magnetic 

 characteristics of steel and other magnetic materials. In accuracy 

 it far excels the direct-reading permeameters which have been rather 

 commonly used both in this country and abroad. Normal induction 

 measurements of solid bars show errors no greater than 5 per cent of 

 the magnetizing force required for the given induction. The consistency 

 of its readings taken at different times on the same specimen is so close 

 that comparative results on similar materials can be obtained to a 

 high degree of precision. Commercial materials, however, are seldom 

 uniform enough to warrant better precision than 5 per cent. Hysteresis 

 measurements are accurate within the limits of commercial requirements 

 and the uniformity of commercial materials. C. W. B. 



GEOLOGY. — The inorganic constituents of marine invertebrates. 



Frank Wigglesworth Clarke and Walter Calhoun Wheeler. 



U. S. Geological Survey Professional Paper 102. Pp. 56. 1917. 

 The purpose of this investigation was to determine, more thoroughly 

 than has been attempted hitherto, the character of the contributions 

 made by marine invertebrates to the marine sediments, and therefore 

 to the limestones of oceanic origin, such as shell, coral, crinoidal, etc. 

 Two hundred and fifty analyses were made of the shells or skeletons of 

 organisms ranging from the foraminifera up to the crustaceans, and 

 including, on account of their importance as reef builders, the calcare- 

 ous algae. Each group of organisms was taken in fairly large series, 



