Geological Society of London. 91 



The author then considers that there is proof of the conformity of 

 the qnartzites with the Torridon sandstone, and that there is no 

 unconformity as generally suggested. In this case it appears to 

 hiui to follow that the Torridon sandstone must be either Ordovician 

 or Upper Cambrian in age, and that the former is more probable, as 

 the overlying quartzite is not more than some 500 feet thick, so that 

 the united thickness of the two hardly exceeds at most that of the 

 Arenigs of Shropshire or South Wales. 



2. " The Pre-Cambrian (Archaean) Rocks of Shropshire." Part II. 

 By C. Callaway, Esq., D.Sc, F.G.S. 



The author described the western axis of Archaean rocks in 

 Shropshire, which runs roughly parallel with the Wrekin and 

 Caradoc ranges at a distance of from six to seven miles, the inter- 

 vening district being chiefly occupied by the Longraynd rocks. 

 The_y are exposed over a line about 11 miles long, forming usually 

 low hills or ridges trending S.S.W. Pontsford Hill, however, at the 

 northern end projects prominently into the Shropshire plain. In the 

 lower part of this hill are purple rhyolites banded and spherulitic, 

 the latter structure being exhibited in chalcedony filling cavities of 

 the rock. Compact dolerite forms the upper part of the hill. At 

 Lyd's Hole a junction of the Cambrian Grits with the underlying 

 rhyolites is seen. Conglomerates containing the latter rock also 

 occur. At Gatten Lodge are purple hornstones ; at Knoll's Ridge 

 somewhat similar rocks, with others that appear intrusive ; at Cold 

 Hill purple hornstone and breccia ; and at Chissol a greenish horn- 

 stone. The rocks of Knoll's Wood are probably about on the 

 horizon of those of Caer Caradoc, grits perhaps derived from a 

 gneissic area. Stratigraphical as well as lithological considerations 

 lead the author to the opinion that the series is Pre-Carabrian. 



3. " The Red Sands of the Arabian Desert." By J. A. Phillips, 

 Esq., F.R.S., F.G.S. 



The author described the general characters of the Nefiid, or great 

 red desert of Northern Arabia, which consists of a series of parallel 

 ridges of considerable elevation, no doubt at some period piled up 

 by the action of strong winds, but now no longer undergoing much 

 change of position, as is evidenced by the fact that sticks and stones 

 remain for many days uncovered on the surface, and that the land- 

 marks made use of in crossing the desert appear to be permanent. 

 A specimen of the sand of this desert received by the author from 

 Lady Anne Blunt, is composed of well-rounded red grains from -aV 

 to 31,- inch in their longest diameter, which are rendered colourless 

 by treatment with hydrochloric acid, the material thus removed 

 amounting to '21 per cent., or a little more than xoo- of the total 

 weight operated upon, and consisting of ferric oxide with a small 

 quantity of alumina. The sand dried after the action of hydro- 

 chloric acid gave on analysis : — 



Silica 98-63 



Protoxide of iron 0*28 



Alumina 0-88 



Lime, magnesia, and alkalies trace. 



99-69 



