192 Correspondence — R. L. Sherlock — E. M. Anderson. 



February 19, 1915, awarded liim the Lyell Geological Fund in 

 recognition of liis valuable work on the fossils of the Derby and 

 ^Nottinghamshire Coal-field, including his contribution to the 

 recently published Geological Survey memoir on that district. 



That so valuable a life as tbat of our friend Dr. Lewis Moysey 

 should have been sacrificed in so sad and tragic a manner, though in 

 the service of his country, only increases our sorrow for his 

 premature loss to science and to his personal friends, by whom he 

 was greatlv valued.] 



E. A. N. A. 



OOI^K,E!SI=OITXDEl]SrCE!. 



"FLINT-MEAL" FROM THE BRITISH CHALK. 



Sir, — I should be greatly obliged if any of your readers would 

 send me properly localized samples of flint-meal from the British 

 Chalk, other than the B. mucronata zone of Norfolk, of which I have 

 plenty. Failing flint-meal, weathered chalk containing foraminifeia 

 is useful provided its horizon is known. 



R. L. Shekloce:. 



Geological Survey, 



Jermyn Street, S.W. 1. 

 February 25, 1918. 



A NOTE ON ISOSTASY. 



Sir, — A rather important consideration has, I think, been over- 

 looked by Dr. A. Morley Davies (see Geol. Mag. for March, p. 125). 

 In estimating the amount of subsidence that must ensue "if the 

 isostatic adjustment is perfect and immediate " after a sea of 

 depth d has been filled to the surface with sediment, we must take 

 into account not only the weight of sediment but also the weight of 

 water which flows in over the sediment during the process of sinking. 

 Allowing for this on the basis of Dr. Davies' figures, the downward 



movement becomes — - — d. To secure equilibrium, with sedimenta- 

 tion up to sea-level, we have the following equation, where x is the 

 total subsidence : — 



lQ6d -f 2-36x = 3x. 



1-36 , 



■or the total thickness of sediment = 3-12 <^, instead of I'SSd as 

 calculated by Dr. Davies. If we assume for the density of the 

 substratum what we may agree is the rather unlikely figure of 2-7, 

 the last result is altered to 5 d. 



E. M. Anderson. 

 Edinburgh. 



March 11, 1918. 



