330 Reports & Proceedings — Geological Society of London. 



by the colour of its chemical compounds and the high-temperature 

 specific heats of platinum, silica, and the alkali felspars. 



Three papers deal with glass. One of them, by N. L. Bowen, is 

 entitled "The significance of Glass-making to the Petrologist". The 

 summary given is as follows : — 



Contrary to certain claims that have been made, glass-making processes 

 offer no support to the belief in liquid immiscibility among silicates, nor to the 

 belief in a significant density stratification in a mass wholly liquid. They do, 

 however, suggest the importance of gravity acting on a mass partly solid and 

 partly liquid, and emphasize two stages : (1) that at which there is much 

 liquid and little solid, and (2) that at which there is little liquid and much 

 solid. In magmas these two stages are probably those during which the most 

 significant results in the way of differentiation are accomplished. 



Bowen's paper is a valuable contribution to a difficult subject. 

 Field experience, especially in Mull, has led the present reviewer to 

 favour the opinion that gabbro and granophyre are sometimes 

 immiscible for a sbort range of temperature before crystallization sets 

 in in earnest. Evidence pointing in this direction is often wanting 

 even in the field, and under certain experimental conditions it 

 might well be absent, owing, for instance, to such complications as 

 metastable miscibility. 



Various other papers treat the side of penological inquiry that 

 receives its inspiration from the writings of Willard Gibbs. Thus, 

 G. A. Rankin and H. E. Merwin illustrate the temperature- 

 concentration relations of the various crystalline phases in equi- 

 librium with liquid in the ternary system MgO — A1 2 3 — Si0 2 . 

 Arising from this we find a reinvestigation of the melting points and 

 stability relations of cristobalite and tridymite, carried out by 

 John B. Ferguson and H. E. Merwin. Cristobalite is confirmed in 

 its claim to be the high-temperature form of silica. 



Ferguson also gives an account of the equilibrium relations of the 

 volcanic gases C0 2 , CO, S0 2 , and S 2 . 



Henry S. Washington has quite a number of papers to his credit. 

 Three refer to Italy, and include a consideration of the leucitic lavas 

 as a potential source of potash. Of his other works may be mentioned 

 a compilation and discussion of chemical analyses of igneous rocks, 

 1884 to 1913, and a new edition of his Manual of the Chemical 

 Analysis of Rocks. He also gives an account of a method of 

 calculating from chemical analyses of clays the mineral composition 

 "generally quartz, felspar, and kaolin". No novel principle is 

 involved, but the procedure is recommended as "of great simplicity 

 ■and accuracy". E. B. Bailey. 



EEPOETS ^.nXTID ZPZEtOOZEJEnDIHSTG-S- 



I. — Geological Society oe London. 

 May 21, 1919.— Mr. G. W. Lamplugh, F.R.S., President, in the 



Chair. 

 The following communications were read : — 



1. "The Silurian Pocks of May Hill." By Charles Irving 

 Gardiner, M.A., F.G.S. With an appendix by Frederick Richard 

 Cowper Reed, Sc.D., F.G.S. 



