SECTIONAL TRANSACTIONS.—C. 381 
by purchased specimens and by contributions collected by past and present 
students. 
Among those who have qualified in Geology from this school some have 
proceeded to the University, others to Training Colleges, mining schools, 
while others have entered business life. The examination results have 
been excellent: for example, this year 13 pupils obtained their Higher 
Certificate; of these, 7 took Geology, 5 passing with distinction and 2 with 
credit. 
There is some prejudice, however, against the teaching of Geology, and 
it is hoped that one of the results of this discussion will be to remove this 
and give Geology a fair chance of surviving on its own merits. 
Prof. A. H. Cox, Prof. A. E. Gittican, Prof. W. W. Watts, F.R.S., 
and others. 
AFTERNOON, 
Excursion to Corton, Scratby and the Broads (2.15). 
Wednesday, September 11. 
Mr. J. H. TayLtor.—The use of heavy minerals in correlating igneous rocks 
(10.0). 
The communication gives a summary of the results achieved in an 
examination of the validity of the correlation of intrusive igneous rocks by 
means of their accessory minerals as elaborated in a series of papers by 
Dr. A. W. Groves, who dealt in particular with the Armorican intrusives of 
South-West England, the Channel Islands and the Cotentin. American 
interest in the subject is evidenced by the appointment of a committee of 
the National Research Council to deal with the subject, but as yet the opinion 
_ of the members seems to be divided. 
The author has thoroughly tested the hypothesis by examining the 
Tertiary granites of northern Ireland and elsewhere, applying quantitative 
methods involving counting all the heavy non-magnetic accessories and the 
several types of zircon and apatite. In the large composite intrusion of the 
Mourne Mountains the following results have been reached : 
(a) Rocks of the four members of the complex are individually distinctive 
as regards their major constituents and texture ; but cases are recorded in 
which rocks of the same petrographic type yield dissimilar accessory suites, 
while rocks dissimilar in type and belonging to different members of the 
complex yield similar accessory suites. 
(6) Samples from different parts of any one member of the complex 
vary considerably in regard to the mineral species present, their varietal 
characters and relative proportions. 
(c) The vertical distribution of zircon and fluorite has been carefully 
examined and it is evident that the depth of erosion has an appreciable 
effect upon the proportions and varieties of these minerals. 
Finally, by comparison of the granites of the Mourne Mountains with 
others, both Tertiary and older, it is concluded that the Tertiary granites 
cannot be separated by their accessory minerals alone from those of other ages. 
Dr. A. T. J. Dottar.—The geology of Ailsa Craig (10.30). 
Ailsa Craig, at the south end of the Firth of Clyde, is a heterogeneous 
mass of riebeckite microgranite (the ailsyte of Prof. N. F. Heddle), cut by 
a swarm of basic dykes. Special interest attaches to the sedimentary 
