Correspondence — Mr, S. V. Woody Jun. 45 



to be the cause of those features attaching to the Combrash upon 

 which Mr. Green relies. The irregularity of the Pre-glacial surface 

 is indicated by the outcrop at Lillingstone Dayrell of the older 

 rocks, without the intervention of the bed No. 2, the gravel ; that 

 bed coming in again in great force under Whittlebury, three miles 

 beyond the northern end of my section. It is impossible that the 



1. The Great Oolite and Combrash concealed except where the valleys cut down to it. 2. Gravel 

 and sand with boulder beds (the Middle Glacial), being bed No. 1, of Mr. Green's section. 

 3. The Upper Glacial clay • — - Valley deposits, alluvium, etc. N.B. The Oxford clay may 

 come in at the South end of the section under No. 2, but if so it is wholly concealed. 



The junction-line of 2 and 3 should be level instead of undulating as made by the engraver on one 

 side of the Ouse. 



Base-line about 200 feet above the sea. Vertical scale about 500 feet to the inch. Length of section 

 six miles. 



Post-glacial valley system should not frequently encounter these 

 irregularities of Pre-glacial surface, which are thus made use of 

 to found an argument for the Pre-glacial origin of our present 

 valleys in the South. The main charge that I bring against this 

 part of Sheet 45, and the Memoir accompanying it, is that both 

 omit all reference to that which, having regard to its super- 

 ficies and original thickness, is the greatest Tertiary formation 

 of England, in point of magnitude — the Glacial clay. But few of 

 your readers may be aware that, although the gravel given in Mr. 

 Green's section is copiously illustrated, and this, as well as the 

 valley beds, and even the alluvium, are described in the memoir, 

 not the least allusion, either in map or memoir, is made to the 

 Glacial clay. The result is that, not only this part of Sheet 45 E, 

 but the greater part of Sheet 52, nearly half of Sheet 46 W, and part 

 of Sheet 53, are delineated in a merely conjectural manner. Had 

 this great formation not been thus ignored, I cannot conceive that 

 the Geological surveyors would have failed to recognize that the 

 valley of the Ouse, from the source of that river above Buckingham 

 to its debouchure upon the Fen country, was, as Mr. Prestwich had 

 shown it to be about Bedford, formed subsequently to the Glacial 

 clay. S. V. Wood, Jun. 



P.S. — In his letter Mr. Dawkins says, in reference to the brick- 

 earths in the Eailway cutting immediately to the North of Mile-end 

 Terrace, and half-a-mile from Hill-house (which I have mapped as 

 a part of the Dartford -heath brick-earth, and treated as identical 

 with those of Crayford, Erith, and Ilford, which Mr. Dawkins 

 regards as synchronous), that "the fact that they contain nearly 

 all the testacea now living in our rivers, and none of those extinct 



