Reports and Proceedings — Mineralogical Society. 42^ 



conditions of cooling are such that the magma becomes super- 

 saturated with one mineral after another, it will overshoot the 

 eutectic composition before each crystallises, and the final consoli- 

 dation may be a well-marked sequence instead of a simultaneous 

 crystallisation. 



The controversies which have raged concerning the classification 

 of rocks and their nomenclature appear to me to contribute little to 

 the real advancement of knowledge. There are, I think, two mora 

 profitable lines of research which should accompany each other. 

 We may take the facts as we find them, and endeavour to explain 

 them by the known laws of solutions aided by the phase-rule, 

 provided that we have good reason to believe that rock-magmas 

 behave like solutions, and we may make experiments upon slags and 

 fused silicates and ascertain how far they resemble natural rocks in 

 their behaviour and their mineral constitution. Some of the workers 

 in this field have been led to regard rock-magmas as undoubtedly 

 similar to ordinary solutions ; others hesitate to seek an explanation 

 for their features in the laws which govern the solutions studied in 

 the laboratory. The two views are represented in the persons of 

 the two men whose names are most closely identified with recent 

 experiments, Vogt of Christiania and Doelter of Graz. 



{To he continued.) 



II. — Mineralogical Society of London. 

 Mineralogical Society, June 14th, 1905. Professor H. A. Miers,. 

 F.R.S., President, in the chair. — The Chemical Composition of 

 Lengenbachite, by Mr. A. Hutchinson. A quantitative analysis of 

 the new mineral from the Binnenthal, recently described by R. H.- 

 Solly, leads to the formula 7 Pb S, 2 As2 S3, part of the lead being 

 replaced by silver and copper and part of the arsenic by antimony. — 

 The Chemical Composition of Hutchinsonite, by Mr. G. T. Prior. 

 Chemical examination of this new and extremely rare mineral from 

 the Binnenthal, described by E. H. Solly, showed that it could be added 

 to crookesite and lorandite as a third mineral containing the rare 

 element thallium as an important constituent. Quantitative analysis, 

 made on a small amount of material (about 70 mgr.), showed the 

 presence of about 20 per cent, of thallium and suggested the formula 

 (Tl, Cu, Ag)3 S As2 S3 + Pb S Asa S3.— The identity of the Amiantos 

 of the Ancients with Chrysotile, by Dr. J. W. Evans. The principal 

 source of amiantos appears to have been Cyprus. Specimens brought 

 by Prof. Wyndham Dunstan from the ancient workings on the slopes 

 of Mount Troodos prove to be chrysotile and not tremolite asbestos. 

 - A chemical analysis by G. S. Blake confirmed this result. — Gnomonic 

 Projection on two Planes at Eight Angles, by Dr. J. W. Evans. By- 

 means of these projections and the rotation of one plane on an axis 

 at right angles to the other, simple solutions of cry stall ographic 

 problems are obtained, — The President exhibited supersaturated 

 solutions of sodium nitrate, showing the transition from the metastable 

 condition, in which crystallisation is only possible in the presence of 

 solid crystals, to the labile condition, in which the liquid can 

 crystallise spontaneously. 



