270 GILLIGAN : ALLUVIAL DEPOSITS AT WOODLESFORD, ETC. 
effervescence when treated with hydrochloric acid. They vary great- 
ly in the number of laminae to the inch, this being a fmiction of their 
fineness. 
Clays from various localities were taken and, after being dried at 
100 deg. C. and finely powdered, were treated with cold dilute hy- 
drochloric acid, when the following results were obtained : — 
Percentage 
Insol. in HCl. 
Woodlesford 89*5 
Eothwell Haigh 87-6 
Victoria Cave . . . . . . 86*5 
Danby (Cleveland) .. .. 834 
Robin Hood's Bay . . . . 82-2 
Brickfield, south east of York . . 72*0 
A sample of lacustrine clay of glacial origin from Wisconsin, 
kindly forwarded to me by Prof. Leverett, gave 69-24 % insoluble 
in dilute hydrochloric acid. 
The presence of irregular masses of carbonate of lime, and also of 
rhombohedral crystals of calcite has already been mentioned. So 
that it would seem that calcium carbonate (if all the soluble portion be 
reckoned as such) is an important constituent of all these clays. It is 
probable that the waters of the lakes contained a large percentage of 
calcium carbonate in solution — for it need hardly be pointed out that 
limestone forms much of the area from which the ice came, and also 
that calcium carbonate is more soluble in cold water than in warm. It 
is probable also that much of this calcium carbonate in the clays was 
originally secreted from the lake waters by algae, of which no traces 
remain. 
The finding of the laminated clay in the washpools at Eothwell 
Haigh and Newlay suggested the experiment of washing the sands 
from these deposits in the laboratory and allowing the fine material to 
settle. It was formd that the resulting fine material gave a deposit 
consisting of a lower lighter and an upper darker layer, for every 
separate wash. Working with boulder clay from Rothwell Haigh it 
was found that it yielded all the material of the sands and gravels as 
well as the laminated clay. The heavy minerals were also the same 
though monazite was not found in such abundance as in the sands. 
