176 
LAMPLUGH : GLACIAL BEDS. 
The next clay, which forms the lower part only of the 
division known as the Purple Clay of Mr. S. Y. "Wood, is, as 
I have attempted to show, clearly divided from the overlying 
Boulder clay, not only by its lithological characters, — for 
those I put out of the question for the present, — but by the 
evidence of a denuded surface, which admits into its hollows 
gravels and laminated clays of great thickness, — in one case 
a mass of the latter being over thirty feet thick, a deposit 
which must have required a long time to accumulate. 
The Brown Boulder clay, which comes next in succession, 
is separated from the top Red Band by gravels, more or less 
continuous, which are in one place at least 30 feet thick, and 
which sometimes admit into their midst a distinct band of 
dark Boulder clay, which, though it does not continue far, 
clearly shows that time must have elapsed between the forma- 
tion of the one and the other. 
In this estimate of the value of these lines of division, I 
have purposely omitted all reference to the well-marked 
lithological differences, such as in colour and texture, and 
in the quantity and character of the included boulders ; and 
to the palseontological distinctions, in the comparative abun- 
dance, or rarity, of shell fragments, as effects like these 
might have been caused by changes in the direction or con- 
ditions of the ice-flow. 
But when these points are taken in conjunction with the 
presence of the intercalated beds which I have just recapitu- 
lated, it seems to me that the sum of evidence thus obtained 
shows clearly that these beds could not have been accumulated 
by a continuous and unbroken period of ice-action. 
It also shows that there are lines whose claims have been 
hitherto overlooked, which may be quite as worthily used in 
dividing these clays as any of those now acknowledged. 
It remains to be proved by further research which are the 
most important of these divisions, but I think it will be found 
