STUDY OF ORES AND METALS. 447 



and solvents, color, density, hardness, etc., in addition to the deter- 

 mination of the degree of anisotropism. 



In this paper the properties of a number of opaque substances 

 such as ores and metals, determined by the several methods de- 

 scribed above, are not included ; such lists would add materially to its 

 length and are not germane to its purpose. 

 Geophysical Laboratory, 



Carnegie Institution of Washington, 

 Washington, D. C, 

 March i, 1917. 



