iS8 Geological Remarks aa the 



sinkings of various new wells, (on sonve of which I have 

 been consulted) near the metropolis, have exhibited less of 

 rtgularitv in the succession and thicknesses of the strata, 

 than I had been led to expect: also, that at Alford in Lin- 

 cohishire, where numerous very shallow wells are sunk and 

 holes in them bored, through this clay and the sand under 

 it into the chalk, from whence the water rises and perpe- 

 tually overflow's the surface, I fonnd this clay and sand 

 niuch thinner than it usually is about London. It is my 

 wish, to suspend entirely my opinion on the above interest- 

 ing questions, until many more facts are collected, and 

 especially until the situations ofour principal assemblages of 

 fossil shells above the chalk at Hordel, Reading, Woolwich, 

 in the shell marles of Suffolk, &c. he. are ascertained, and 

 they have been examined and minutely described by a com- 

 petent conchologist^ and. such descriptions have been care- 

 fully con) pared with tho^drawings and details by our author* 

 and M. Lamarck :, an; undertaking which 1 wish nmch to 

 press on the innncdiate attention of the societies above 

 mentioned. 



If no part of the qhalk be elevated more than 50 feet 

 above the Seine (p. 43), it should seem probable, that the 

 50 chalk fossils mentioned (p. 42) belong to about only 

 one-eighth of the whole thickness of the chalk strata, at 

 its top. 



In commencing a very extensive Mineralogical Survey, 

 like Mr. Smith's manuscript Map of England, Wales, and 

 part of Scotland, it will perhaps be best to foliow his exam- 

 ple, in selecting only such strata as usually form distinct 

 ranges of hills through tlie country, by their bold or sudden 

 endmgs, to form his classes or principal assemblages of 

 strata, that are to be distinguished each by a different co- 

 lour in his Map and Sections, without much regarding the 

 mineral characters, or characteristic fossils of the several 

 thin strata that compose each of them, leaving these to be 

 enumerated and described in written details and in local 

 sections on a large scaler In commencing more local, but 

 yet considerable surveys, such as my square of map includ- 

 ing Derbyshire, or the basin of Paris, the bold endings of 

 particular strata ought 1 thinlv still to have a principal share 

 in determining the selection of such as are to have a difier- 

 cnt colour assigned to them; the other considerations slu^uld 

 be the width or extent of surface which is made by the se- 

 veral strata, and the distinct mineral characters of particular 

 thick strata or beds: a few thin beds or strata which hap- 

 pen t«j have very striking character^ cither in their appear- 

 ance. 



