wherry: native element minerals 447 



each prism showed curvature of 5' the differences should be 

 regarded as observational. The difference 4 e-co is probably not 

 in error more than ±0.001. 



A recent notice of a study of the physical properties of car- 

 borundum by 0. Weigel has been published, 5 but no details are 

 available. 



MINERALOGY. — The nomenclature and classification of the 

 native element minerals. Edgar T. Wherry, 1 National 

 Museum. 



In many respects it would be difficult to improve upon the 

 nomenclature and classification of native elements worked out 

 in Dana's System of Mineralogy, yet with the advance of scientific 

 knowledge new points of view are certain to arise and newly dis- 

 covered species to demand place in any scheme, so that changes 

 must be introduced. A few suggestions in this direction are 

 here put forward, for discussion, criticism, or whatever fate they 

 may seem to readers to deserve. 



nomenclature 



The names adopted by Dana are as a rule satisfactory, but 

 wherever considerations of simplicity, consistency, and clearness 

 suggest the desirability of changes from his usage, there should 

 be no hesitation about introducing others. 



When an element is known to occur in nature in but one form, 

 no name different from that used for it in chemistry is needed; 

 but several elements show polymorphous forms, and these have 

 heretofore been distinguished by adding either: a suffix, as in 

 sulfur and sulfun'/e; a prefix, as in palladium and a7fopalladium ; 

 Greek letters as prefixes, as in a-sulfur and /3-sulfur; or adjectives, 

 as in yellow phosphorus and monoclinic selenium. The last method, 

 using crystallographic adjectives, is preferable, because it can be 

 employed alike in all cases, and its systematic introduction 

 into mineralogical nomenclature is therefore recommended. 



4 The value for the D-line was checked on a thinner plate and, roughly for 

 lithium light, on grains in immersion liquids. 

 MVeigel, O. Chem. Abstr., 11: 1066. 1917. 

 transferred August 16th to the Bureau of Chemistry. 



