MANCHESTER GEOLOGICAL SOCIETY. 
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of lime ; for, when treated with, hydrochloric acid, it effervesces. 
The clay, when cut down, shows its brown colour ; but when 
allowed to cleave in the open air vertically and horizontally, as 
it will do when in the act of di'ying, the sides of the cleavages 
are coated with a covering of dull blue colour, probably arising 
from the presence of carbonate of iron. In it are mingled with- 
out any order of position, blocks of red and light-colured gi-a- 
niteSj sienites, porphyries, greenstones, basalts, and various 
other igneous rocks; slates of different descriptions, silurian 
rocks, mountain jlimestones, cherts, millstone grits, all the in- 
durated rocks and coals of the carboniferous series, and magne- 
sian limestones ; but no rocks of a more modern date have as yet 
been found in it. These fragments are of various sizes, from 
the size of a pea to blocks of five tons in weight, lying mingled 
together, without any order of deposition. The external cha- 
racters of the rocks in this clay near Manchester are very re- 
markable; some present well rounded surfaces, whilst others 
are angular, as if they had been just separated from their parent 
rocks, having scarcely undergone any attrition. The Scotch 
porphyries, the red granites of Shap, and the light-coloured ones 
of Ravenglass, and other parts of Cumberland, with various 
greenstones and basalts, and all the hard slate rocks, none of 
which are found in situ within a less distance than near 100 
miles, are for the most part well rounded, and some of them 
scored with striae. The mountain limestones are more angular ; 
but the millstone grits, coal measure strata, and magnesian lime- 
stones, have nearly always sharp edges. All the great boulders 
which are seen lymg about the surface in various parts of this 
district, are probably from this deposit of till, as I have never 
yet seen any excavated from other deposits. 
There was a number of specimens on the table of these boul- 
ders, &c. picked from one of the clay-pits. The magnesian lime- 
stone could not have come many miles ; others were peices of the 
common coal measure flags, quite sharp, as if they had under- 
