144 Geological Society: — 



Shropshire, which runs roughly parallel with the "Wrekin and 

 Caradoc ranges at a distance of from 6 to 7 miles, the intervening 

 district being chiefly occupied by the Longmynd rocks. They 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 rhyohtes 

 is seen. Conglomerates containing the latter rock also occur. At 

 Gatten Lodge are purple hornstones ; at Knoll's Eidge somewhat 

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

 purple hornstone and breccia ; and at Chissol a greenish hornstone. 

 The rocks of Knolls 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 Precambrian. 



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

 Esq., F.P.S., F.G.S. 



The author described the general characters of the Nefud, 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 under- 

 going 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 landmarks 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 J- to -±- 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 -^ 

 of the total weight operated upon, and consisting of ferric oxide 

 with a small quantity of alumina. The sand dried after the action 

 of hydrochloric acid gave on analysis : — 



Silica 98-53 



Protoxide of iron 0-28 



Alumina 0*88 



Lime, magnesia, and alkalies trace. 



99-69 



The external coating of ferric oxide must therefore have been 

 deposited subsequently to the rounding of the grains; it could 

 not have been derived from an external decomposition of the grains 

 themselves ; and it becomes difficult to imagine in what manner the 

 superficial red coating can have been produced. The author com- 

 pared these grains with those of the millet-seed sandstones of 



