MINERALOGY. 669 



ployed. It consists, briefly, of a Wollaston goniometer and a lever ar- 

 rangement attached to the stand, which brings a tine point down to the 

 plane to be measured. By use of the lever each of the planes can be 

 adjusted so that its surface is perpendicular to their index, and then the 

 angle between the planes is given in the usual way ; in a word the touch 

 of the index takes the place of the reflection to the eye in fixing the 

 position of the two planes in succession. 



The stauroscope, the degree of accuracy it admits of, and the kind of 

 errors it involves, is the subject of a somewhat diffuse paper by Las- 

 peyres (Zeitsch. Eryst., yiii, 97). He claims for the instrument a high 

 degree of accuracy, but shows that there are certain unavoidable errors 

 which limit its use as the instruments are now constructed. 



CHEMICAL MINERALOGY. 



The subject of the artificial production of minerals continues to be 

 one to which many contributions are being made, particularly by the 

 French chemists. Bourgeois (Bull. Soc. Min. France, vi, 64) describes 

 the production of crystallized rhodonite by fusing together silica and 

 manganese dioxide. Gorgeu has obtained (lb., p. 13G) hausmannite in 

 brilliant octahedral crystals by the aid of manganese chloride kept 

 fused at a red heat in an oxidizing atmosphere charged with water 

 vapor. The same author (1 b., p. 2S3) has succeeded in forming, by the 

 synthetic method, the manganese garnet, spessartite. Lacroix (lb., 

 173, 175) describes artificial crystals of gypsum, and also crystals of 

 cerussite, which had formed in bronze coins of Boinau origin found iu 

 Algeria. 



Two important pa]>ers bearing upon the paragenesis of certain me- 

 tallic minerals have been presented by Le Conte (Amer. Jour. Sc, xxv, 

 424; xxvi, 1). In one of them he describes the mineral vein formation — 

 chief in interest the cinnabar deposits — which is now in progress at 

 Steamboat Springs, in Nevada, thus following up an earlier paper on 

 the phenomena observed at Sulphur Bank. The locality at Steamboat 

 Springs has already been the object of extended papers by Laur iu the 

 Annates des Mines, 1803, and by Phillips in the Quarterly Journal of the 

 Geological Society of London, 1879. The phenomena at Sulphur Bank 

 and Steamboat Springs are in some respects very similar, though iu 

 others they are quite different. At Steamboat Springs the deposit of 

 silica is much more extended, as explained by the fact that the hot 

 waters contain mainly alkaline carbonates which carry silica in solution, 

 while at Sulphur Bank they contain also largely alkaline sulphides and 

 carry metallic sulphides in solution. In the second paper Le Conte dis- 

 cusses iu general the genesis of metalliferous veins, arriving at various 

 interesting conclusions in regard to them ; they are in part a confirma- 

 tion of earlier results reached by others. 



Of the many papers dealing with chemical composition of the differ- 

 ent mineral species, the most important is that of Tscherinak (Sitzber. Ak, 



