﻿Vol. 64.] CHANNEL OF DRIFT AT HITCHIN. 17 



Thichiess. Depth in feet. 



Existing dug well (mostly brick-earth ) 64 



Loamy ballast 3 ^7 



Live blue sand 20 87 



Sandy clay and stones 90 



Sandy ballast 36.1 126^ 



Sandy clay ^ 129^ 



Clay, stones, and small pieces of chalk 6^ 136 



Stiffclay 5 141 



Sandy clay and sand , 7 148 



Sand 16 164 



Stiffclayand stones (some lignite, 169 tol77 feet). 32 196 



Clayey sand 10 206 



Clay and stones 4 210 



Very hard sand 7 217 



Live sand 29^ 246^ 



Sand and stones 26:^ 273 



Stony clay 2U 294^ 



Blowing sand 4 298^ 



Stony clay 14| 313^ 



Clayey sand, stones, and small pieces of chalk... 4 317 



Blue sandy clay , 15 332 



Sandy clay and stones 8 340 



Gault 5 345 



Here it will be seen that 340 feet of Drift was encountered, and 

 the Chalk was absent altogether. I was fortunately present when 

 the auger brought up Gault, a stiff dark-blue clay : in my judgment, 

 it was not the top of the Gault. At Arlesey the upper 20 feet or 

 so is paler in colour than that lower down, and I think that the 

 Gault touched in this boring was below the upper and paler part of 

 it. JN'othing like Cambridge Greensand was passed through, and I 

 examined very carefully the material which had been brought up by 

 the auger. 



Another boring here deserves attention. The great thickness of 

 Drift encountered at Mr. Eansom's brickyard led me to consider a 

 boring made at Messrs. Lucas & Co.'s brewery in Hitchin in the year 

 1831, the details of which are given in the ' Geology of the London 

 Basin.' ^ After having passed through 80 feet of surface-soil and sand, 

 149 feet of white and grey marl was pierced before reaching the 

 Gault. It will be noticed that Mr. Whitaker questions the identity 

 of this white marl with the Chalk. The mouth of this boring was 

 about 220 feet above O.D., and it must have been commenced just 

 below the Melbourn Rock. As there is not more than 170 feet of 

 Lower Chalk in this locality, Gault should have been reached at 

 that depth at least ; but it was not touched until 229 feet, which 

 puts the base of the Chalk 60 feet lower than it should be and gives 

 it a thickness of some 225 feet. It will be seen that the surface of 

 the Gault was at nearly the same height above sea-level in both 

 borings. I am inclined to think, and I believe that Mr. Whitaker 

 agrees with me, that much of the white and grey marl mentioned 

 in this boring may be Drift. 



1 Mem. Geol. Surv. vol. iv (1872) p. 453. 

 Q. J. G. S. No. 253. c 



