310 MINERALOGY. 



done in these directions. The results of such studies, if of interest in 

 detail to but few (and they are treated with utmost detail), must not be 

 underestimated, for they tend toward a better understanding of molecu- 

 lar structure, a knowledge of which may at any time prove of utmost 

 interest to all. 



3£ica. — Prof. G. Tschermak, who, as is well known, has made a most 

 valuable investigation upon micas, the results of which proved that all 

 micas are mouocliuic in form and that they possess variable optical 

 properties which necessitated a redivision and to a certain extent a new 

 nomenclature, has now, with the aid of Sepocz, extended his examina- 

 tion to the brittle micas of the clintonite group. These he finds also to 

 be monoclinic, and possessed of optical properties that make it possible 

 to systematize them in the same way as the elastic micas. Thus our 

 knowledge of a large number of minerals which before were very imper- 

 fectly understood has been much improved. 



ARTIFICIAL MINERALS. 



The synthetic methods of study have always found especial favor in 

 France. The imjietus given by the men who have so distinguished 

 themselves in this way has in the past year brought forward a number 

 of new studies, almost all of them French. 



Daubree's new book upon experimental geology contains an account 

 of all his previous experiments, and noticeable are the methods that he 

 has used to make sublimed minerals. The book is very interesting to 

 read, though its chief merit is the bringing together in condensed and 

 accessible form all the distributed writings of the author upon these 

 subjects. 



Fouque, who some time since succeeded in reproducing the feldspars 

 by the simple process of allowing fused mixtures to slowly cool, has by 

 the same process made leucite, nephelin, and a variety of rocks that 

 ate comi)osed of minerals arranged in the same way, and scarcely dis- 

 tinguishable from volcanic products. These results both have a geolog- 

 ical interest, and are noticed in that section. 



Fouque and Levy performed the very pretty experiment of fusing 

 a mixture of scapolite and hornblende, and obtained by slow cooling 

 a mixture of labradorite and i^yroxene. One recalls the old experiment 

 of ]Mitscherlich, who fifty years ago fused hornblende and obtained py- 

 roxene. One of the very interesting experiments of Fouque and Levy 

 recently performed was that by which they produced feldspars of vari- 

 ous degrees of acidity, in which lead, baryta, or strontia were made to 

 take the place of the bases ordinarily found in them. 



Velain has examined microscopically the fused ashes of grasses and 

 other i)lants, and found in them tridymite, anorthite, wollastonite, and 

 augite. Professor Maskelyn has described an artificial diopside rock 

 formed in a Bessemer steel converter. Liebetheuite, the copper phos- 



