348 James Croll — On the Glacial Epoch. 



been the cause of the Glacial epoch, yet we can, as we have just 

 seen, easily understand how the ice of the Glacial epoch could have 

 been the cause of the submergence. If the Glacial epoch was brought 

 about by an increase in the eccentricity of the earth's orbit, then a 

 submergence of the land as the ice accumulated was a physical 

 necessity. 



There is another circumstance connected with Glacial submergence 

 which it is difScult to reconcile with the idea that it resulted from a 

 subsidence of the land. It is well known that during the Glacial 

 epoch the land was not once under water only, but several times ; 

 and, besides, there were not merely several periods when the land 

 stood at a lower level in relation to the sea than at present, but there 

 were also several periods when it stood at a much higher level than 

 now. And this holds true, not merely of our own country, but of 

 every country on the northern hemisphere where glaciation has yet 

 been found. All this follows as a necessary consequence from the 

 theory that the oscillations of sea-level resulted from the trans- 

 ference of the ice from the one hemisphere to the other ; but it is 

 wholly inconsistent with the idea that they resulted from upheavals 

 and subsidence of the land during a very recent period. 



But this is not all, there is more still to be accounted for. It has 

 been the prevailing opinion that at the time when the land was 

 covered with ice, it stood at a much greater elevation than at present. 

 It is, however, not maintained that the facts of geology establish 

 such a conclusion. The greater elevation of the land is simply 

 assumed as an hypothesis to account for the cold (Phil. Mag. for 

 Nov. 1868, p. 376). The facts of geology, however, are fast 

 establishing the opposite conclusion, viz. that when the country was 

 covered with ice, the land stood in relation to the sea at a lower level 

 than at present, and that the continental periods or times when the 

 land stood in relation to the sea at a higher level than now were the 

 warm interglacial periods, when the country was free of snow and 

 ice, and a mild and equable condition of climate prevailed. This is 

 the conclusion towards which we are being led by the more recent 

 revelations of surface geology, and also by certain facts connected 

 with the geographical distribution of plants and animals during the 

 Glacial epoch. 



The simple occurrence of a rise and fall of the land in relation to 

 the sea-level in one or in two countries during the Glacial epoch, 

 would not necessarily imply any physical connexion. The coinci- 

 dence of these movements with the glaciation of the land might have 

 been purely accidental ; but when we find that a succession of such 

 movements occurred, not merely in one or in two countries, but in 

 every glaciated country where proper observations have been made, 

 we are forced to the conclusion that the connexion between the two 

 is not accidental, but the result of some fixed cause. 



If we admit that an increase in the eccentricity of the earth's 

 orbit was the cause of the Glacial epoch, then we must admit that all 

 those results followed as necessary consequences. For if the Glacial 

 epoch lasted for upwards of one hundred thousand years or so, there 



