Reports and Proceedings — Geological Society of London. 129 



Mineralogy," a new edition of which has just appeared. We cannot 

 help feeling some regret that in a work on determinative mineralogy 

 the author has felt compelled to omit even a brief account of one of 

 our most important aids in the identification of minerals. As 

 a manual for the chemical determination of minerals, the older 

 editions of Brush's work could be regarded as complete ; but with 

 the introduction of a chapter on crystallography in the present 

 edition, the character of the work is so far changed that as a manual 

 of determinative mineralogy it appears incomplete without a chapter 

 on the optical properties of minerals. 



The tables for the identification of minerals at the end of the book, 

 originally founded on those of Von Kobell, have been brought up to 

 date and completely rearranged : they are intended to include all 

 well-characterized species at present known. G. T. P. 



E-ZB^^oiRTS j^:isriD i='ie,OGE!:Bx:)i3:Nrc3-s. 



Geological Society of London. 



L— January 18, 1899.— W. Whitaker, B.A., F.R.S., President, in the 

 Chair. The following communications were read : — 



1. "On a small Section of Felsitic Lavas and Tufi"s near Conway 

 (North Wales)." By Frank Ptutley, Esq., F.G.S. 



The rocks described in this communication were collected in 

 1877, in series, at short intervals, from a point at the mouth of the 

 Eiver Conway near Bodlondeb.' They consist of felsitic lavas and 

 tuffs, sometimes nodular, and generally exhibiting some variety of 

 fluxion-structure, corrugated, or banded. A specimen showing 

 brown bands is compared with one described by Iddings from 

 the Yellowstone Park. What were once possibly red bands are 

 now represented by devitrified brown glass, and the change in 

 colour may have been due to the action of water upon the ferric 

 oxide which originally gave its colour to the glass. Some of the 

 rhyolites are tufaceous, and envelop fragments of rocks, some of 

 which were originally vitreous, others lithoidal. Coarser rhyolitio 

 tuff occurs at the northern end of the series. 



2. " The Geology of Southern Morocco and the Atlas Mountains." 

 By the late Joseph Thomson, Esq. (Communicated by the 

 President.) 



This paper gives the results of observations made under con- 

 siderable difficulties during a journey in Morocco in 1888. The 

 tract traversed is roughly triangular, the base being the Atlantic 

 Ocean between Saflfi and Agadir, and the apex the district of Denanat 

 on the northern slopes of the Atlas, some sixty miles east of the city 

 of Morocco. This district consists of three main sections : (1) The 

 Coast Lowlands ; (2) the Plateau in two chief steps, the northern 

 rising to 2,000 and the southern to 5,000 feet: (3) the Atlas itself, 

 which only begins to be a mountain-chain about thirty miles from 

 the coast, and which ranges first east-by-north and then north-east 

 in its central and loftiest part. 



DECADE IT. VOL. A'l. — ^NO. III. 9 



