INDUSTRIAL PROGRESS DURING THE YEAR 187G. Ixxxv 



mined the coefficient of elasticity of rods of rock-salt by a series of 

 delicate acoustical experiments. These rods were cut in different 

 directions from the crystal of salt, and the main result arrived at is 

 the proof that the elasticity has difterent values in different direc- 

 tions, but the same value in all directions crystallographically iden- 

 tical, 



Baumhauer has continued his researches upon the figures produced 

 upon the surfaces of crystals of lepidolite, tourmaline, and other min- 

 erals by means of various modes of etching. The same method of 

 investigation has proved, in his hands, that crystals of mimetite and 

 pyromorphite are hemihedrally developed in the same way as those 

 of apatite, though it is not apparent in their external forms. 



The accurate measurements of crystals of analcite by Schrauf have 

 led him to the conclusion that it, like leucite, must be transferred to 

 the list of tetragonal crystals (instead of isometric). It is claimed, 

 however, by Hirschwald that both species are truly isometric, though 

 showing the phenomena of " polysymmetry." Tschermak has also 

 shown that the common mica, muscovite, is monoclinic, not ortho- 

 rhombic. 



The crystals of chondrodite from Brewster, N, Y,, have been 

 shown by an American crystallographer to embrace the same three 

 types of forms that characterize the volcanic mineral humite, of 

 Vesuvius ; moreover, the oj^tical characters of the second and third 

 types show them to be monoclinic^ though they do not agree between 

 themselves. Des Cloizeaux has supplemented these observations by 

 a like examination of the Vesuvian mineral (humite), and has thus 

 shown that the three types must be considered three distinct species ; 

 which he proposes to call respectively humite^ chondrodite^ and clino- 

 humite. 



A number of new and strange cases of the association in parallel 

 position of crystals of two distinct species have been described ; 

 thus, j)yroxene on hornblende, humite on chrysolite, etc. The most 

 remarkable case is that of quartz on calcite, an interesting form of 

 which has been figured from " Specimen Mountain," in the Yellow- 

 stone National Park, 



A related though quite different subject is the inclosure of one 

 crystal by another, as the strange envelojiment of orthoclase by tour- 

 maline described by E, II, AVilliams {Amer. Journal of Science^ Feb., 

 1876), The i^resence of liquid carbon dioxide in minerals has been 

 confirmed by Hartley, and some new facts in regard to it published. 

 His studies have led him to suggest the idea that diamonds may 

 have been formed by the action of reducing agents on very highly 

 compressed carbon dioxide. Dr. Isaac Lea has continued his study 

 of the inclusions, both liquid and solid, by some gems, as sapphire, 

 spinel, etc. 



The new localities of American minerals, spoken of in the last vol- 



