IN THE QUATERNARY PERIOD. 419 



Ramsay's estimate of 800 feet more, that elevation being 

 required for the deposition of some of the stratified drift, we 

 must demand an additional period of 32,000 years, amounting 

 in all to 88,000 ; and the same time would be required for 

 re-elevation of the tract to its present height. But if the 

 land rose in the second continental period no more than 600 

 feet above the present level, this .... would have taken ano- 

 ther 24,000 years ; the whole of the grand oscillation, com- 

 prising the submergence and re-emergence, having taken, in 

 round numbers, 224,000 years for its completion ; and this, 

 even if there were no pause or stationary period, when the 

 downward movement ceased, and before it was converted into 

 an upward one." 



To most geologists these figures, large as they are, will have 

 no appearance of improbability. All the facts of geology tend 

 to indicate an antiquity of which we are but beginning to 

 form a dim idea. Take, for instance, one single formation 

 our well-known chalk. This consists entirely of shells and 

 fragments of shells deposited at the bottom of an ancient sea, 

 far away from any continent. Such a progress as this must 

 be very slow : probably we should be much above the mark 

 if we were to assume a rate of deposition of ten inches in 

 a century. Now the chalk is more than a thousand feet 

 in thickness, and would have required therefore more than 

 120,000 years for its formation. The fossiliferous beds of 

 Great Britain, as a whole, are more than 70,000 feet in thick- 

 ness ; and many which with us measure only a few inches, 

 on the Continent expand into strata of immense depth ; while 

 others of great importance elsewhere are wholly wanting with 

 us ; for it is evident that during all the different periods in 

 which Great Britain has been dry land, strata have been 

 forming (as is, for example, the case now) elsewhere, and not 

 with us. Moreover, we must remember that many of the 

 strata now existing have been formed at the expense of older 



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