330 Prof. Frankland on the Physical Cause 



winter, yet the corresponding heavy fall of rain in summer would 

 again liquefy the excess of snow so deposited. In reply to this 

 objection, it might perhaps be sufficient to oppose the facts above 

 given, regarding the comparative height of the snow-line in ad- 

 jacent moist and dry localities ; but I may also add in explanation 

 of these facts, that a comparatively very large quantity of even 

 warm water is required to melt snow or ice. In fact, as is well 

 known, the amount of heat requisite merely to melt them would^ 

 if no melting occurred, raise their temperature to 174° F. Let 

 us suppose that upon any given ice-bearer the precipitation 

 throughout the entire year was doubled, that during six months 

 of the year this increased precipitation occurred in the form of 

 snow at 32° F., and that during the remaining six months it fell 

 in the form of rain at 50° F. ; still, even with these conditions, 

 so manifestly unfair towards the ice-bearer, very little more than 

 one-eighth of the additional snow would be melted by the warm 

 rain. In fact it requires nearly eight tons of water at 50° F. to 

 melt one ton of snow or ice, even when the latter is already in a 

 thawing condition. Forbes considers that not more than one- 

 fiftieth of the snow upon the snow-fields of Norway is liquefied 

 by the rains of summer ; whilst M. Durocher has calculated, from 

 observations made at the convent of St. Bernard in Switzerland, 

 which is slightly below the snow-line, that not more than one- 

 ninetieth of the annual snow is dissolved by the rain. Thus the 

 effect of summer rain in melting the snows of winter is compa- 

 ratively insignificant. 



2. Is it not a necessary consequence of this hypothesis that 

 the ocean must have possessed a temperature incompatible with 

 animal life at the comparatively remote protozoic period ? This 

 question doubtless raises the most formidable of the objections that 

 can be brought against my view ; nevertheless there are several 

 considerations which deprive it of much of its force. Judging 

 from purely geological evidence, the period which has elapsed 

 since marine life first made its appearance, compared with that in- 

 tervening between the glacial epoch and the present time, would 

 probably not be under-estimated at 1000 :_1 ; consequently it 

 would appear to be evident that if the ocean has cooled through, 

 say 20° F. during a unit of time, it must have been at a boiling- 

 temperature at a far less distant period than 1000 such units. 

 There are three circumstances, however, which forbid such an 

 unqualified deduction. In the first place, the excessive evapo- 

 ration of water at temperatures not far removed from the boiling- 

 point would rapidly reduce the ocean and its floor to a compara- 

 tively moderate temperature. Secondly, the excessive precipita- 

 tion which must have occurred in the preglacial periods must 

 have accelerated the deposition of most of the sedimentary rocks 



