476 SECTIONAL TRANSACTIONS.—C. 
so named because it marks the dividing line between the Middle and 
Lower Cambrian in which Prof. Lapworth was greatly interested. The 
deposit is black, phosphatic, and calcareous, about 3 inches thick at its best, 
and crowded with brachiopods (Acrothyra) and Hyolithellus micans.. The 
little Lapworthella shells are abundant. There are also three or more other 
organisms and some nodular bodies, probably algal in origin. 
This limestone occurs in the same stratigraphical position at Rushton. 
‘TRANSACTIONS AT THE LEICESTER MEETING. 
Thursday, September 7. 
PRESIDENTIAL ADDRESS by Prof. W. G. FEaRNsIDzES, F.R.S., on A correlation 
of structures in the Coalfields of the Midland Province (10.0). (See 
P- 57:) 
Mr. H. H. Grecory.—The geology of the Leicester district (11.0). 
Mr. Francis Jones.—Further notes on the petrology of the igneous rocks 
of Leicestershire (12.30). 
The intrusive rocks of the Leicestershire-Warwickshire area group into 
five divisions, viz. (1) Diorite-Granophyres of Charnwood, (2) Micro- 
diorites of South-West Leicestershire, (3) Mountsorrel Granite complex, 
(4) Camptonite-Diorites of Nuneaton, (5) Intrusions into Caldecote series. 
Chronological or genetic correlation is difficult. The age of the last two 
groups is known within limits : that of the granophyres is established with 
the fifth group. The ‘ camptonites’ contrast with all the others not only 
as regards basicity, but in being concordant intrusions of ‘ wet ’ magma. 
~ Structural study of the Mountsorrel complex confirms the evidence of 
its mineral freshness that it is a late intrusion. The isolated outcrops of 
the non-granophyric diorites of the south-west make special difficulty in 
interpreting their position in the sequence. Joint phenomena suggest 
structures excluding contemporaneity with the granophyres. Mineralogi- 
cally they ‘ fit in’ between the granophyres and the granite. They show 
diversity of detail mainly in regard to hydrothermal alteration and to the 
occurrence of epidote. The Croft-Huncote rock is of especial interest in 
regard to the former. Here albitisation is advanced : analcite and laumon- 
tite have been developed as vein minerals, and prehnite occurs within the 
altered rock. The phenomena developed resemble those described by 
Gilluly in his paper ‘ Replacement Origin of the Albite Granite, Sparta, 
Oregon ’ (U.S. Geol. Sur. Prof. Paper, 175-C). 
AFTERNOON, 
Excursion 1: Demonstration of geophysical methods in the field. 
Leaders: Dr. A. F. Hatitrmonp, Mr. A. T. J. DoLvar. 
Excursion 2: The glacial geology of the Leicester district. Leaders: 
Mr. W. Keay and Mr. Martin GIMson. 
Yes ry 
- 
he ee ee ee 
