PROCEEDINGS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. Cxlvii 
is greater richness and depth. The proportion of peroxide of 
iron has also increased. The supply of sand is constantly being 
replenished by the decay of the sandstones below, and coatings of 
argillaceous material, in a fine state of sub-division, are added from 
time to time by the floodings of the rivers. Towards the slopes of 
the volcanic hills, such as the Sidlaws and Ochils, the soils of the 
plain are enriched by the admixture of the earthy salts already 
referred to. In the Carse of Gowrie, the soil consists nearly entirely 
of clay, representing the finest and lightest material carried by the 
river, and therefore the last to be deposited in the course of its 
gradually diminished velocity. This material, which is sometimes 
described as the “ Flour of Rocks,” represents the finest of the debris 
of all the rocks in the drainage area of the river, but with most of the 
sand or free silica sifted out, owing to its greater specific gravity. 
Chemically, it is a fairly rich soil, although the proportion of silicate 
of alumina is probably rather high, owing to the other silicates having 
been largely dissolved away. Mechanically, however, it is too com¬ 
pact and retentive to be very suitable for cultivation without a good 
deal of amelioration. 
In the foregoing sketch of the Perthshire soils, I have left out of 
account one important factor, namely, the boulder clay, which is 
pretty widely distributed through the different districts. This I have 
done for the sake of simplicity, but the general conclusions are not 
very much affected thereby, as the boulder clay reflects pretty much 
the characters of the water-borne material, though rather differently 
distributed. If time had permitted I should also have liked to touch 
upon the deposits left by silted-up lakes, the soil of peat mosses, and 
the accumulation of ancient river deposits; but my object has been 
to point out, by means of local examples, the principles which under¬ 
lie the study of soils, rather than to give an exhaustive description 
of the soils of the district. The subject is one which has been too 
long neglected by geologists, who have studied with minute care all 
the rocks which go to form the earth’s crust, but have too often 
dismissed with a mere passing remark the cap of loose material 
which covers so large a proportion of the surface of that crust. 
6th April, 1897. 
Henry Coates, F.R.S.E., President, in the Chair. 
The following donations were intimated :— 
Library —Year Book of the U.S. Department of Agriculture— 
from the Smithsonian Institute. Handbook of the Norwich Museum 
—from the Curator. Photographs of Trees in Winter—from Mr. 
W. Ellison. 
John Minto, M.A., Librarian (Sandeman Public Library); James 
Alexander, Muirhall Terrace; and Miss Hannah Gold, LL.A., Alyth, 
were elected Ordinary Members. 
