EVIDENCES OF THE AGE OF ICE. 
Ill 
Another feature of the surface-geology of the country dates 
from the same period — the widely- distributed boulder-clay, or 
“ till.” This deposit is not at all likely to be confounded with 
any other. It consists of a mass of unstratified clay, with blocks 
and boulders of stone stuck into it promiscuously, the whole 
seeming to be the result of an irregular “ pell-mell ” carrying 
forward and deposition of the materials (see figs. 1 and 2). 
The colour and general composition of the mass may vary 
according to the nature of the rocks from which it has been 
derived. Thus, in a region of dark Carboniferous shales the boul- 
der clay is leaden, grey, or black ; in one of Old Bed, or Triassic 
sandstones, it is red. In the Chalk country it is quite full of 
bits of chalk, and is hence called the 66 chalky boulder clay.” 
The stones in the clay range in size from mere grains of sand 
up to masses a yard or more in length. Wherever the rock of 
SECTION OF GLACIAL DEPOSITS IN THE SETTLE AND CARLISLE RAILWAY 
CUTTING AT CULGAITH."* 
T, upper till ; S G, sp.nd and gravel ; C, laminated clay ; T', lower till ; JR, rock 
Length, 40 feet. 
which they consist has been of a kind to receive and retain sur- 
face markings, the stones are found to be covered with ruts and 
striae, which run for the most part in the direction of the long 
axis of each stone. 
There can hardly be any doubt that these markings have been 
produced under a sheet of land-ice similar to that which covers 
the whole interior of Greenland at the present day. 
This great inland ice-sheet, that at places advances to the 
coast and thrusts the snouts of its glaciers into the sea itself, 
giving rise to enormous icebergs, covers the entire continent of 
Greenland save a few dozen miles at most of coastline, which 
remain free. It forms on its seaward face precipitous cliffs of 
ice about 200 feet high, covered with a thin layer of earth and 
stones, but rises at first rapidly, afterwards more slowly, to a 
height of several thousand feet. During Professor Norden- 
skiold’s expedition to Greenland in 1870, he made an excursion 
upon this inland ice-sheet with one companion, Dr. Berggen, 
* We are indebted for the loan of this block to the Council of the 
Geological Society. 
