234 Rejjorts and Proceedings — Geological Society of London. 



There are indices to authors, principal subjects, and places. If, 

 however, we want a reference to a memoir, say of Wra. Smith, we 

 must search for it under " Biographies de Geologues — Anglais," in 

 the table or index of principal subjects. If we want a list of works 

 on the geology of Lancashire, we must turn to references under 

 " Grande- Bretagne " in the " Table Geographique." The list of 

 authors is no doubt useful, but we think it would have been 

 much more advantageous to index the Memoir of Wm. Smith under 

 Smith than under John Phillips ; and the list of papers on 

 Lancashire, under Lancashire, rather than under Whitaker and 

 Tiddeman. For ready reference we want, in fact, fuller indices 

 to subjects and places. It is, however, ungracious to find fault 

 with a work that in all other respects is full and accurate. 

 Geologists will do well to turn over the pages of this volume 

 and take note of the books and memoirs that relate to their 

 special subjects of study, and many will be surprised to find 

 how much useful bibliographic work has been done. Of such 

 work no example will probably be more used than the volume 

 before us, and all geologists will feel indebted to M. de Margerie 

 for the great care and labour he has bestowed on the Catalogue. 



i&EJX^OE-TS J^ISTJD IPi^OOIBIEIDIlNra-S. 



Geological Society of London. 



L— March 24, 1897.— Dr. Henry Hicks, F.R.S., President, in 

 the Chair. The following communications were read : — 



1. " Notes on some Volcanic and other Eocks which occur near 

 the Baluchistan -Afghan Frontier, between Chaman and Persia." 

 By Lieut. -General C. A. McMahon, V.P.G.S., and Captain A. H. 

 McMahon, CLE. 



In the first part of this paper Captain McMahon describes briefly 

 the physical geography of the Baluchistan deserts, which extend 

 along the south of the Helmund River, between Quetta and Persia. 

 Taking first the plains and their drainage-system, he shows how 

 the wide alluvial plains of Shorawak and Chagai were probably iu 

 earlier times one large lake. North and west of these plains, as far 

 as Persia, lie vast deserts of sand, which in places are gradually 

 encroaching upon and burying the mountain-ranges which rise up 

 like islands in the desert. He shows how the sand has intercepted 

 all the drainage from the mountains and prevented it from making 

 its way, as it would otherwise do, into the Helmund River and the 

 God-i-Zirreh Lake. Turning next to the mountains, Gapt. McMahon 

 describes a well-defined line of fault, which he traced for a distance 

 of about 120 miles from north of Chaman, along the Khwaja Amraii 

 and Sarlat mountain-ranges to Nushki. East of this fault all the 

 rocks appear to be sedimentary ; while those to the west are all, 

 with few exceptions, volcanic and igneous. 



The mountain-ranges in the desert described appear to be all 

 volcanic, and reference is made to the Koh-i-Taftan, 12,600 feet 

 high, lying south-west of them, which is still an active volcano. 



