182 Reports & Proceedings — Mineralogical Society. 



Although, the text deals largely with engineering problems 

 encountered in the United States, they are identical with those to 

 be met with in any part of the world. 



Some interesting tables and other "information for the drainage 

 engineer are given in the chapter devoted to rivers, relating to the 

 percentage of suspended matter carried by various rivers, which 

 should impress the engineer and student with the desirability of 

 investigating on similar lines the rivers in this country. The same 

 chapter also deals with the ratio of run-off to rainfall, and here again 

 the published information relating to streams in this country is 

 comparatively scarce. 



Excellent chapters are provided on underground water-supplies, 

 road materials, and ore deposits. 



At the end of each chapter is a comprehensive list of references 

 consulted, the majority of \^hicb are the official bulletins of the 

 United States Grovernment, and to these the reader is recommended 

 to refer ; they are published free by the Government at Washington. 



L. E. Wilson. 



REPORTS AND PROCEEDINGS. 



Mineralogical Society. 

 10^^ January. — ^Dr. A. Hutchinson, O.B.E., President, in the chair. 



C. E. TiLLEY : Density, refractivity, and composition-relations 

 of some natural glasses. 



The glasses investigated fall into two groups, (a) tektite glasses, 

 (b) volcanic glasses. The characteristics of the former confirm 

 their divergence from volcanic glasses and support the theory of 

 their meteoritic origin. The specific refractivity of five analysed 

 glasses are compared with the values calculated from the specific 

 refractivities of their component oxides and a notable correspondence 

 is revealed. The influence of contained water on the specific 

 refractivity is discussed and some figures are given bearing on the 

 volume-change accompanying the passage from the vitreous to the 

 crystalline state. 



Dr. H. ,H. Thomas and E. G. Radley : On the so-called 

 " Avanturine " from India, with an analysis of the contained mica. 



The stone is a quartz-schist and owes its colour to j)lates of green 

 fuchsite arranged parallel to the planes of foliation. The mica 

 contauis 1'77 per cent Cr^Og and a little vanadium; its optical 

 characters are described. The probable source of the stone is 

 discussed and its deterioration by heat and other causes is explained. 



A. Russell and A. Hutchinson : On laurionite and paralaurionite 

 from Cornwall. 



Laurionite associated with phosgenite and anglesite in a cavity 

 in limonite is described in a specimen obtained from the collection 

 of John Hawkins, of Trewithin, Cornwall . The locality is probably 



