lastern Boring. 



Difference. 



Feet inches. 



Feet inches 



97 9 



65 8 



203 



' 68 



443 6 



63 6 



Tol. 69.] TWO DEEP BORINGS AT CALVERT STATION. 327 



applied to the various strata passed through are somewhat mis- 

 leading, no useful purpose would be served by reprinting them. 

 Allowing for this difference of 67 feet 8 inches, we find a close 

 agreement in the Jurassic rocks in the two borings ; thus the 

 following datum-lines can be recognized : — 



Western Borhij 

 Feet inches. 

 Base of Oxford Clay... 32 1 



Base of Oolites 135 



Base of Lias 3S0 



Owing to the scant}' nature of the information, however, detailed 

 comparison is impossible ; but the few remarks made in the log- 

 show that the beds generally resemble those of the Eastern Boring. 

 Once below the Jurassic strata, we find a striking difference in the 

 fact that in the Western Boring there was an uprush of inflammable 

 gas, at a pressure of 60 lbs. to the square inch, which is still (June 

 ■1913) escaping, nearly nine years after it was first struck. There 

 has been no trace of gas in the Eastern Boring. 



The sinker's record of the Western Boring gives no details of the 

 strata between 312 and 3S2 feet ; but there can hardly be any 

 •doubt that (as suggested above) the gas had accumulated imme- 

 diately below the base of the Lias at 380 feet. The record gives 

 the following particulars below this level:' — 



Soft red shale. 

 Mottled shale, 2 feet. 

 Mottled shale. 

 Blue shale. 

 Blue"shale. 

 Blue shale. 



Jointy shale and ironstone-bands, 2 feet S inches. 

 Do. do. do. 



The general inference from the above is that, just as in the 

 Eastern Boring, about 50 feet of stained Tremadoc Shales were 

 rjassed through, and then the typical grey shale was reached. This 

 is confirmed by the fact that, when the boring was re-started 

 in 1911, the first material brought up w r as a very mixed-up sort of 

 red mud, doubtless derived from the soft red or mottled shales at 

 and below 382 feet. When this was washed, a sandy residue was 

 left, quite like that from the mottled shales of the Eastern Boring. 

 Cores were got from 456 feet 6 inches down to 649 feet, and 

 all those that we have seen were essentially similar to the Tre- 

 madoc Shales of the Eastern Boring. Eossils were not abundant, 

 but the following were found : — 



Obolella (I) aff . salteri Holl, at 500, 515, 520, 523, and 524 feet respectively. 

 Clonograptus (fragments), at 523 feet. 



Two questions arise out of a comparison of the two borings : — 



(1) Is it possible to determine the strike of the Tremadoc Beds ? 



(2) What is the source of the gas in the Western Boring? 

 Q. J. G. S. No. 274. z 



Feet 



inches. 



382 







413 







433 







434 



7 



437 



7 



443 



7 



440 







445 



8 



