232 



PREHISTORIC EUROPE. 



M. Colloinb estimated at 15,000 square kilometres, but which 

 is actually under the truth) discharged its water at the same 

 rate, it must have yielded a daily supply of 605 millions of cubic 

 metres. But if it be true, as all the facts would lead us to 

 believe, that in the summers of the Glacial Period more heat 

 was received directly from the sun, — then the daily discharge 

 from such a glacier must have been greatly in excess of that 

 amount. 



The rivers which escape directly from a glacier are invariably 

 turbid and discoloured with the fine mud which they hold in 

 suspension, this sediment being derived from the pounding and 

 grinding of the rocks under the moving ice. MM. Dolfus and 

 Desor found that a litre of water from the Aar glacier con- 

 tained 0'142 gram, of fine mud, so that according to Collomb's 

 estimate of the area and daily discharge of the ancient Ehone 

 glacier, the water escaping from the latter must in summer 

 time have transported 86,000,000 kilogrammes, or about 8500 

 tons (English) per diem — an estimate which, considering the 

 circumstances already referred to, is probably much under the 

 actual truth. 1 



Bearing all this in mind, we are prepared to learn that traces 

 of water-action should be met with at very considerable heights 



1 According to Helland the quantity of mud in the rivers that issue from the 

 glaciers of Greenland is very variable, as may be seen from the table given by 

 him, which is as follows : — 



River of the glacier of Jakobshavn 

 ,, ,, Alangordlek 



,, ,, Ilardlek 



, , , , Tuaparsuit 



, , , , Umiatorlik 



,, ,, Rangerdlugssuak 



Similar observations by the same geologist on the water issuing from the snow- 

 and ice-field of Justedalsbreeen likewise showed that the quantity of mud varied 

 in the different streams, and even in the same river. The result of ten different 

 observations in the months of June and July gave a mean of 147"9 grams, of mud 

 in 1 cubic metre of water.— See Quart. Joum. Oeol. Soc, 1877, p. 157 ; Om'de 

 isfyldte Fjorde og de glaciate Dannelser i Nordgronland, p. 53j Geol. Foreningens 

 i Stockholm Forh., Bd. ii. No. 7. 



