Correspondence — J. Smith — A. Sfrahan. 479 



One would have thought that enough had been said already about 

 the zones of the Chalk, and that especial pains would therefore be 

 taken to attain to greater exactness in official memoirs. 



C. Davies Sherborn. 



MARINE SHELLS. 

 Sir, — 1 beg to inform the readers of the Geological Magazine 

 that, acting under my directions, Mr. David Nimmo, jun., and 

 Mr. Frank White have found marine shells in the drift of the Leaze 

 Burn, near the watershed with Logan Water, and four miles north- 

 east of Muirkirk, in Ayrshire. The drift here is a yellowish 

 Boulder-clay, the clay being very fine-grained and exceedingly 

 suitable for preserving organisms. The exposed bed is 15 feet thick, 

 rock not seen, and 1,330 feet above sea-level, and is the highest 

 point in Scotland at which marine organisms have been found in 

 the drift. J. Smith. 



MONKREDDING, KiLWINNIXG. 



Sept. 1, 1902. 



DEVELOPMENT OF EIVEES. 



Sir, — Mr. Buckman, in his article on Eiver Development in the 

 August number of the Gteological Magazine, criticizes my paper 

 published in the Quart. Journ. Geol. Soc, vol. Iviii, p. 207. On 

 two points his criticisms are well founded. My allusion to the 

 Vale of Moreton, which was added after the writing of the paper, 

 was made under a misapprehension, for I had not grasped the fact 

 that the anticline was considered by Mr. Buckman to be of Inferior 

 Oolite age. Under such circumstances it was of no use to me, for 

 I was in search of an arching up of the Chalk at a much later date. 

 It is true also that the Vale of Moreton is wrongly placed on my 

 map. The name was added, I think, on a proof, but the responsibility, 

 of course, was mine. As regards the other points on which 

 Mr. Buckman considers that I have erred in matter of fact, I see 

 no reason to modify what I wrote. 



Mr. Buckman finds it very remarkable that the anticline of which 

 I was in search should be evidenced by no more than traces. The 

 difficulty in locating it is due to the fact that the Chalk, in which 

 alone its effects would have been obvious, has been denuded away ; 

 that it has not been recognized in the Oolitic rocks means nothing, 

 for it would be masked by the more pronounced movements which 

 affected those rocks before the deposition of the Chalk, but that 

 it existed is proved by a general consideration of the dip of such 

 Chalk as remains. As I pointed out, the westerly rise cannot have 

 continued indefinitely, for it would have carried the Upper Cretaceous 

 base far above the level at which we believe it to have lain in the 

 West of England and in Wales. 



The paper by Mr. Buckman in the Proc. Cottes wold Nat., vol. xiii, 

 p. 175, 1899-1901, which I characterized in a footnote as " trans- 

 gressing the limits of legitimate speculation," was preceded, as he 

 points out, by a paper in Natural Science, vol. xiv, p. 270, 1899. 



