484 SECTIONAL TRANSACTIONS.—C. 
of marked climatic difference between the highland source area and the 
area of deposition leads to the conclusion that the red coloration is only in 
part due to dehydration in the arid Permian climate, but mostly to detrital 
iron oxide formed in the monsoonal conditions of the Upper Carboniferous. - 
Prof. D. M. S. Watson, F.R.S. 
The speaker reviews the evidence afforded by the contemporaneous 
fauna as to the conditions in which the red beds were formed. 
Mr. J. H. Taytor.—Contribution to the petrology of the Mountsorrel 
igneous complex (12.0). 
The paper deals with two aspects of the complex which have received 
little attention : (1) the nature and characteristics of the accessory minerals ; 
and (2) the processes by which the several members of the complex were 
formed and emplaced. 
Under (1) some twenty mineral species are recorded from the area and 
described in detail, particular attention being given to the widespread and 
varied zircon and apatite. Points of special significance are the corrosion 
of many of the zircons, and the occurrence of dark, sometimes almost 
black, apatites. 
Under (2) the view is expressed that both granodiorite and quartz-mica 
diorite are of hybrid origin, resulting from the action of acid magma on 
basic rock. The latter was almost certainly the gabbro of Swithland 
reservoir, while some indication of the nature of the acid magma is afforded 
by a thin marginal facies of the granodiorite that has the composition of 
alkali granite. "The granodiorite was formed below present ground level, 
and was subsequently injected into the position it now occupies. 
Three new chemical analyses are quoted and discussed, and comparisons 
are made with rocks of the Channel Islands, Dartmoor and the Isle of Man. 
Dr. F. Raw.—On the Triassic and Pleistocene surfaces developed on some 
Leicestershire igneous rocks (12.15). 
The well-known grooved and polished surfaces exhibited by some of the 
Leicestershire igneous rocks have long been regarded as dating from the 
Triassic period, and as bearing evidence of formation by natural sand- 
blasting under desert conditions. The author has reached the conclusion 
that these features are here due to the Pleistocene glaciation. 
AFTERNOON. 
Excursion to the granite area of Mountsorrel. Leaders: Mr. H. H. 
Grecory, Dr. E, E. Lowe. 
Wednesday, Septémber 13. 
Dr. L. S. B. Leaxey.—The age of part of the Rift Valley in Kenya (10.0). © 
In East Africa, work during the past seven years has thrown much new 
light upon the age of the Great Rift Valley, which was formerly considered 
to be an event of Mio-Pliocene age, with only small secondary movements 
during the Pleistocene. 
