JST. 41.] ROYAL SOCIETY. 91 



1853 was the date of his election into the Royal 

 Society, an honour prized by every man who has done 

 original work. Prestwich's certificate of candidature 

 for the Royal Society was signed by Lyell, De la Beche, 

 Murchison, Edward Forbes, Ramsay, Daniel Sharpe, 

 Bowerbank, John Phillips, W. B. Carpenter, George 

 Busk, and Huxley. 



J. Prestwich to Sir Charles Lyell. BRISTOL, IBth November 1853. 



MY DEAR SIR CHARLES, I am hardly yet prepared to answer 

 your inquiries so distinctly as I could wish. " The Drift " 

 question is so beset with difficulties, and is of such extent, that 

 I cannot venture to bring it forward at one time, but I shall, as 

 with my Tertiary papers, discuss each stage of it separately. I 

 hope, therefore, that you will have returned before I bring for- 

 ward the "Denudation of the Weald," as on that point I should 

 particularly wish to have the advantage of your discussion. In 

 many of Mr Trimmer's views I quite agree, such as two or three 

 periods of gravel-spread, the more recent date of the mammalifer- 

 ous beds of the Thames valley as compared with the boulder 

 clay, &c., but in many others I differ. The one to which you 

 allude viz., the extent of denudation at this first period of sub- 

 sidence I cannot agree in. The denudation of the Chalk evi- 

 dently commenced at the commencement of the Maestricht 

 period, and was continued through the period of the Thanet 

 Sands to that of the London Clay. During this long interval it 

 seems to me that the Chalk over the Weald was planed down to 

 a mere shell, and in many places worn away, so that the work 

 of denudation left to be done at the more recent "drift" period 

 was comparatively small. But even in this period I do not 

 believe that it was all done at once there is, I think, on the 

 contrary, evidence of several successive clearances. 



At the same time, unlike the slow wearing away of the older 

 Eocene period, I believe these recent changes to have been sudden 

 and violent in their operation. Not having my books with me, 

 I can hardly make the references which I could wish. My 

 section (No. 8, Quart. Journ. Geol. Soc., vol. viii. p. 258) is, as 



