88 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 17, 



nomena. The reception of such a theory must always be accom- 

 panied with great reserve, and must depend less on its own positive 

 claims, than on an equal or greater want of such claims on the part 

 of rival theories. 



The theory which attributes the changes of terrestrial temperature 

 to a varying configuration of land and sea is scarcely less indefinite 

 than the others in its direct application to account for the difference 

 of temperature between the present and the very remote geological 

 epochs, on account of our ignorance of the disposition of sea and land 

 in any but the most recent geological times. In the more remote 

 periods, more than one of the causes here specified may have had 

 their influence ; but in accounting for the more recent changes of 

 temperature, the last-mentioned theory appears to me to have by far 

 the greatest claim to our attention. I have endeavoured in the pre- 

 ceding Sections of this second Part of my memoir to trace the con- 

 sequences of certain hypothetical configurations of the earth's surface, 

 and to explain the conditions under which a degree of cold might 

 exist adequate to produce the phsenomena of the Glacial Epoch. I 

 propose in this concluding Section to offer a few leading observa- 

 tions on the relative claims of these different hypotheses to our ac- 

 ceptance. 



30. The most obvious mode of producing a great degree of cold is 

 by local elevation. If we attribute the former presumed cold of 

 western Europe to this cause alone, it would be necessary, as I have 

 shown (art. 24, p. 82), to elevate the whole region into a vast moun- 

 tain-range, attaining in some parts theheightof 10,000 feet or upwards. 

 But all geological experience assures us that no such mountain-range 

 exists without numerous dislocations and other phsenomena of ele- 

 vation having determinate relations to the elevated tract. Of such 

 characteristic phsenomena not the slightest traces have been recog- 

 nized. If it be urged that the elevation might be more local than 

 here supposed, I would reply that such an hypothesis would rather 

 strengthen than weaken the objection ; for the more local the ele- 

 vation, the more certainly, I think, would it be accompanied with 

 dislocations which could not escape detection. I should reject without 

 hesitation any theory founded on the hypothesis of an elevation during 

 the glacial period, at all approximating to that which would be ne- 

 cessary to produce the required degree of cold. 



3 1 . Again, a great degree of cold might be produced by the con- 

 version of a sufficient portion of the Atlantic into dry land. But this 

 would also require an elevation of western Europe, probably of several 

 thousand feet (art. 25). Now if the cold of the glacial epoch were 

 thus produced, this enormous area of the Atlantic must have been 

 uplifted from its former level immediately previous to that epoch, 

 and must since have again subsided. Considering the probable depth 

 of the Atlantic Ocean, this movement must indeed have been enormous, 

 and yet, although occurring at the most recent geological period, not 

 a trace of it is observable either on the European or American side of 

 the Atlantic. Under any circumstances, a theory founded on such 

 an hypothesis would, I think, be most unsatisfactory, and cannot be 



