198 



ME. W. WHITAKEK OK THE RESULTS 



The Chattenden Boeing, 



Since the publication of my paper the boring at the Chattenden 

 Barracks, northward of Chatham, has been successfully finished. 

 I ventured to say that some 60 feet more (than the 1103 already 

 sunk through) should reach the bottom of the Gault, but that de- 

 sirable result happened in only 59 feet. I did not, however, predict 

 the finding of Lower Greensand here, seeing that there was so little 

 thereof further south at Chatham ; but Lower Greensand has been 

 found, and has yielded the wished for water. 



Having visited the site, seen some specimens, and got further 

 details from Capt. W. W. Robinson, R.E., who had charge of the 

 work, and who has described its progress *, I am now enabled to 

 amplify the last two lines of the former account, as below. 



Chattenden Boring. Details beloiv the Tertiary Beds. 



Thickness 

 in feet. 



Tertiary beds (as before) 290 



Chalk. Specimens of clayey chalk (probably Chalk Marl) 

 at 890, 905, 920, and 940 feet. No springs found. 

 Base not noted. Presumable thickness, judging by 

 the Chatham sections, say : 680 or 682 



Gault, with some pyrites. Specimens, light-coloured clay 

 at 1100 and 1130, the latter with Inoceramus; just 

 above 1140 a Rostellaria ; at 1140 a phosphatic no- 

 dule, with the cast of the whorls of an Ammonite ; 

 about 1140 a small phosphatic nodule, chiefly an 

 Ammonite ; at 1142 dark grey clay. For the last few 

 feet the clay was dark, but with green grains. About 

 9 inches of rock at the bottom (specimen of phos- 

 phatic nodule, from 1161 feet) ? about 192 or 190 



The chisel then dropped 3 feet, and water quickly rose to 

 about 107 feet below the surface, some greenish sand 

 being brought up in the first ebullition. Presumably 

 therefore the Lower Greensand was touched. Sand 

 rose about 60 feet up the tube, and a specimen of the 

 earth being removed (in February 1886) consisted of 

 a mixture of Gault clay with some green sand. 



Depth 

 in feet. 

 290 



972? 



1162 



"When the bottom of the tube was cleared out, and the tubes 

 were driven down into the sand, the water rose to within 100 feet 

 of the surface. 



The almost exact correspondence of the total thickness of the Chalk 

 and the Gault, 872 feet, with the same total at Chatham, where well 

 no. 1 gives the figures 878, and well no. 2 the figures 875, is note- 

 worthy . 



The presence of the Lower Greensand here shows that |in my 

 section (Quart. Journ. Geol. Soc. vol. xlii. pi. iii.), that formation 

 should have been carried a little further north. 



* 'The Royal Engineers' Journal,' vol. xvi. no. 188, pp. 151, 152 (July 1, 

 1886). 



