380 
Frank Carney 
thickness of the upland drift as attested by 210 well records is 
24.6 feet; and so far as 29 borings in the valleys give information 
the depth of drift in the latter area averages 112 feet. This latter 
measurement, however, has slight value since in these lowland 
areas water for domestic purposes is abundant at such slight 
depth that few deeper borings have been made.^^ 
(i) Ground Moraine, Under this heading is included the 
glacial debris of irregular thickness covering the intervals between 
accumulations that mark more permanent halts of the ice. From 
a study of the areas over which the ground moraine is thinnest, it 
appears that the topography is an active factor in its distribution. 
Between the longer dissection axes of the localities where the 
drift is thin, and the direction of striae is a pronounced parallelism. 
This veneer of ground moraine presumably represents the load 
of rubbish carried by the ice that remained when the ice covering 
these areas, in no case very extensive, had become sluggish or 
stagnant, plus any sub-basal drift already accumulated. So long 
as active feeding persisted, the front of the ice probably main- 
tained more or less fixed positions particularly in the region of 
lower altitudes, the valleys. It appears, therefore, that the nor- 
mal outline of the ice-front in the Moravia quadrangle was serrate, 
the divide between the longitudinal valleys being ice-free while 
lobes and tongues occupied the intervening low areas. This ice- 
free condition of the higher regions probably followed a brief 
period during which stagnant or semi-inert ice covered the 
recently freed area. These were periods of less active feeding 
when the melting factor was much the stronger. The ground 
moraine consists largely of such a load of rubbish as this static 
ice contained. Where, however, in certain upland localities we 
find thickened drift, it is evident that the ice receded more slowly 
in consequence of much less inequality between the feeding and 
melting factors, the melting factor being slightly ascendant. In 
such areas it is apparent either that the ice retreated slowly, or that 
it contained a very large amount of rubbish. So far as the investi- 
gation has proceeded we have not been able to find in the topo- 
graphic environment itself a plausible control for thickened drift 
of the uplands. 
The extremes for the well records below the 1300 contour are 45 feet and 300 
feet 6 inches, neither of which reach rock; above this contour the extremes are zero 
and 135 feet. 
