On the Phenomena oj the Glacial Epoch. 243 



America is caused by the water in the Gulf of Mexico, and 

 adjacent parts of the Atlantic, flowing towards the Arctic 

 Sea. It is afterwards deflected eastwards to Europe. By 

 this means it imparts to the western shores of that conti- 

 nent, and more especially to the British Islands, an average 

 temperature higher by many degrees than that which pre- 

 vails in other countries under similar parallels of latitude. 



While the influence of these currents tends, like that of 

 the aerial ones we before referred to, to equalise the tempera- 

 ture of the various regions of the earth, there is this remark- 

 able distinction to be observed between them, — the aerial 

 currents are uniformly distributed over the colder zones, 

 and their influence is generally diffused ; the oceanic cur- 

 rents are limited by the channels in which they flow, and 

 are consequently local in their effects. 



In like manner, as there is nothing to interrupt the course 

 of the heated air, the atmospheric currents continue from 

 age to age unchanged ; while those alterations of relative 

 level, which geology shows us to have been both frequent 

 and great, may alter the channels of the deep, and divert 

 the heated water now to one place and again to another, 

 so that the same locality, which under its influence exhi- 

 bited the verdure of a temperate sphere, may, when that 

 influence is removed, be subjected to the rigours of perpetual 

 snow. 



These conclusions so naturally flow from the acknowledged 

 principles of mechanical philosophy, that we presume there 

 are few who will hesitate to accept of them as correct. 



In examining the different hypotheses that have been ad- 

 vanced on the subject, we find that which is described by 

 Sir C. Lyell, in his " Principles of Geology," and originally 

 brought forward in 1833, more especially entitled to our 

 consideration. " Some," he says, " have been induced to in- 

 fer that there never has been any interruption to the agency 

 of the same uniform laws of change. The same assemblage 

 of general causes, they conceive, may have been sufficient to 

 produce, by their various combinations, the endless diversity 

 of effects of which the shell of the earth lias preserved the 

 memorials; and, consistently with these principles, the re- 



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