ICE OBSERVATIONS. 201 
dilapidated railway embankments. The coarser materials are usually 
more water-worn and the whole more distinctly stratified than in 
moraines, the stratification not seldom exhibiting in transverse sec- 
tions an arched structure, roughly concordant with the exterior of 
the mound. These eskers may sometimes be traced for many miles, 
and commonly, though not invariably, follow the lowest part of a 
valley. The other, called Drumlins, are also mounds, but very dif- 
ferent in shape. Their ground-plan is an oval, the breadth being about 
one-half or two-thirds of the length, which may vary from a few 
hundred feet to a mile, and the height from twenty-five to two hundred 
feet. They are smooth and regular in contour, having steep sides and 
a gently sloping rounded top. The material is a compact clay filled 
with foreign and finely striated stones, very imperfectly, if at all, 
stratified. In any limited area the longer axes of a group are gene- 
rally parallel, and point in the same direction as the glacial striz on 
neighbouring rocks. Supposing either Eskers or Drumlins to exist 
on ice-free portions of the Antarctic land, it will be important to 
observe whether they occur on tracts over which a glacier can be 
proved, by the usual indications, to have passed, together with any- 
thing which may throw light on their relations to it and on the mode 
in which they have been formed. 
