Correspondence — J. E. Marr — R. M. Brydone. 429 



In part xii the author finishes with some " general con- 

 clusions ", but we rather disagree with him that " some con- 

 clusions seem inevitable '". The volume is so essentially a collection 

 and statement of facts that part xii might well have been 

 omitted without much loss, especially as those who will use 

 the book presumably have, or should have, at least a general 

 knowledge of the theories of the origin and concentration of oil 

 and gas. That subject in itself is so extensive and important that 

 to skim lightly over it in a page or two hardly strikes one as in 

 keeping with the rest of the volume. As is essential to a book of 

 this nature it is well indexed, which adds materially to its value 

 as a work of reference. 



The publishers are to be congratulated on the printing and 

 general style of the book, though here and there exception might 

 be taken to the j)roof-reading, which has been by no means perfect. 



CORRESPONDENCE, 



S. B. J. SKERTCHLY'S STONE IMPLEMENTS. 



Sir, — I am anxious to trace the implements obtained by the late 

 Mr. S. B. J. Skertchly from deposits of the districts around Brandon 

 and Mildenhall, which he claimed to be of mid-Glacial age. 



I should be glad if anyone in possession of any of these would 

 kindly inform me of the fact, giving all details concerning the labels, 

 and if possible, outline-figures of the specimens. 



I trust that you will be able to help me by inserting this letter in 

 the Geological Magazine. 



John E. Maep.. 



Sedgwick Museum, Cambridge. 

 Augusts, 192G. 



LINGULA IN THE CHALK. 

 Sir, — Mr. G. W. Butler will find published records, now of some 

 standing, in Brydone's Stratigraphy and Fauna of the Trimmingham 

 Chalk (London : Dulau & Co., 1900), and in Griffith & Brydone's 

 Zones of the Chalk in Hants (London : Dulau & Co., 1911). At 

 Trimingham it "has been found both in the white chalk and in the 

 grey chalk. 



E. M. Brydone. 

 27 Maybury Mansions, 



Marylebone Street, W. 1. 

 Juhj 24, 1920. 



PHYSIOGRAPHIC RELATIONS OF LATERITE. 

 Sir, — At the end of his article in the May number of the Magazine 

 Mr. F. Dixey gave a summary of the conditions affecting lateritiza- 

 tion in Sierra Leone, but did not include a physiographic factor 



