494 TRANSACTIONS OF SECTION C, 
In one of the excavations carried to a depth of 29 inches there also occurred 
immediately beneath the turf a definite layer of white even-sized wind-worn 
sand, the grains measuring about 3, inch in diameter, above the fine red sand 
with wind-worn stones. 
The occurrence of wind-worn stones is also recorded from other localities 
in the Midlands, and specimens in illustration were exhibited. 
WEDNESDAY, SEPTEMBER 17, 
The following Papers and Reports were read :— 
1. On the Classification of Igneous Rocks. By H. Warn, D.Sc. 
The classification I have suggested is based entirely on the chemical compo- 
sition of the rocks in molecular proportions. On the strength of averages 
obtained from one thousand selected rocks sixfold repeated dichotomous division 
yielded sixty-four groups of intimately related rocks. By means of the factors 
obtained any other rock may be assigned to its respective group. A diagram 
demonstrates the relations of the groups to each other, and, moreover, a tetra- 
gonal projection shows the limits within which all possible combinations of acid 
and basic rock constituents are confined. 
As similarly composed rocks generally form similar minerals, the majority 
of the rocks of each group are also mineralogically alike. It cannot be stated too 
strongly that the customary division of igneous rocks into acid, intermediate, 
basic, &c., is clearly also a chemical classification. The subsequent grouping into 
families and species is based upon mineralogical differences. 
The method now proposed carries the classification on a chemical basis very 
much further, and accordingly brings the rocks in each of the sixty-four groups 
so much closer together. 
Should it in time be found expedient to establish on similar principles a com- 
plete quantitative classification on exclusively mineralogical basis the two systems 
would most appropriately mutually supplement each other, notwithstanding 
a certain amount of overlapping. 
2. On the Presence of Copper in the Sandstones of Exmouth. 
By Crom, Carus-Wiuson, F.R.S.E., F.G.S, 
The cliff section along the shore to the east of Exmouth golf links shows the 
red marls, with intercalated sandstones, and these were examined last winter 
to a point just beyond the High Lands of Orcombe. The sandstone was found 
to contain copper-carbonate. This is widely distributed, and shows itself as 
bright green patches upon the rock. Its presence is due to copper pyrites, 
which occurs as one of the mineral constituents of the sandstone, and which is 
undergoing decomposition. The sandstone is chiefly made up of rounded quartz 
and carnelian grains, bound together by a cement composed of the carbonates of 
lime and magnesia. There is also much manganese present. The grains of 
quartz give evidence of having been rounded by wind-action, and subsequently 
smoothed and polished by fine material suspended in water. They possess the 
conditions which, when accumulated on the beach, and sifted by wind and 
wave-action, are favourable to the production of musical sands, and several 
patches were found. Owing to the large percentage of lime and magnesia 
present in the springs issuing from the cliffs, and the precipitation of this on 
the evaporation of the water, much of the beach material footing the cliffs in 
places has been, and is now being, consolidated into masses of recent sandstone 
and conglomerate. 
The presence of copper, carnelian, manganese, &c., indicates chemical and 
mineralogical conditions similar to those prevailing during the deposition of 
the German Rothliegendes. 
