Solar Energy in Belatio7i to Ice. 151 



the surface, where, sooner or later, it again tumbles into a 

 crevasse, melts its way to the surface, and so on until the 

 advance of the ice has carried it to the terminal moraine. 

 This principle enables us to explain how it has happened 

 that stones have so often been transported by ice to levels 

 higher than that of their parent masses, often by many 

 hundreds of feet, of which so many examples are to be found 

 in Scotland and elsewhere. The extent to which a stone 

 may be elevated by this cause is limited only by the thick- 

 ness to which the enclosing ice attains. It is this cause 

 which, during the Glacial Period, elevated organisms which 

 had become enveloped in frozen mud, to positions often a 

 thousand or more feet above that of their starting-point, and 

 which has given rise to so firm a belief — still held by many 

 whose opinions are entitled to respect — that there was a 

 great submergence during the Glacial Period. I endeavoured 

 to show, in a paper in the Geological Magazine for November 

 1874, that organisms could be elevated within the ice in 

 this manner (not pushed before it, as careless or prejudiced 

 writers have represented me to say), and subsequently left 

 at these higher levels when the ice melted. It is this same 

 property that stones in ice possess which has made fragments 

 of coal, oil-shale, or other dark carbonaceous materials, melt 

 their way up in the ice, and which, when the ice came to 

 melt, contributed to their being sorted apart from other 

 stones in the water- worn materials that form Eskers. 



But this warming of stones within the ice produces a result 

 of even greater importance. If heat be communicated to ice, 

 the ice expands ; and if the expansion arises from the heat 

 radiated from a large number of stones, such as are known 

 to exist in the lower parts of many glaciers — notably in those 

 of Greenland and Alaska — this expansion must be a very 

 important factor in propelling forward the part of the ice in 

 which the stones occur. Furthermore, as I have pointed out 

 in one of the communications above rafeired to, the heat that 

 is constantly flowing outwards from the Earth itself enters 

 the ice at all parts where the ice and the rock are in contact. 

 There must necessarily ensue from the conjoined action of 

 these two sources of heat a considerable amount of expansion. 



