"Vol. 69.] TWO DEEP BOEINGS AT CALVERT STATION. 333 



from some part of the Lower Oolites at Oxford, and from the 

 Corallian in many places, 1 as well as from the Kellaways Hock. 

 As to (2), the comparison seems to be based upon the engineer's 

 description only, no specimen of the Bletchley rock having been 

 preserved. As to (3), we read that 



' all the larger specimens were broken up by the chisel ; those preserved are 

 chiefly fragments of the stems and arms of small crinoids, with several pieces 

 of small beleumites and fragments of bivalve shells,' 



which might quite well be Liassic. 



On the other hand, Prof. P. P. Kendall has pointed out 2 the 



'difficulties involved in any attempt to interpret this boring and to bring it 

 into accord with the . . . bprings at Stony Stratford. . . . These two borings ' 

 [he remarks] 'indicate the presence of a normal series of Oolite and Lias 

 within 5 miles of the Bletchley boring, and the intervening distance, 

 5 miles, is insufficient to explain the absence of at least some of the beds 

 at Bletchley, just as the normal dip of the Oxford Clay in the district would 

 not account for the presence of so great a thickness of the Oxfordian beds. 

 I suspect that some beds of greater geological age than the Oxford Clay occur 

 in the lower part of the Bletchley borehole.' 



To the difficulties pointed out by Prof. Kendall, we would add the 

 ■lifchic character of Nos. 9-13. In these beds, which on the usual 

 interpretation are in the middle of the Oxford Clay, out of a total 

 thickness of 33 feet, 18 feet 9 inches consist of oolitic and crystal- 

 line limestones. These invite comparison with the Porest Marble 

 •of the Calverc Boring, and we suggest the following correlation of 

 ■the two borings : — 



Calvert. Bletchley. 



Feet inches. Feet. 



Oxford Clay 93 3 192 



Forest Marble 38 9 33 



Great Oolite, etc 67 absent? 



Lias (Charmouthian) ... 240 6 185 



This new interpretation dispels the difficulties pointed out by 

 Prof. Kendall, and justifies his suspicion that older rocks than 

 Oxford Clay were present. We may also now feel more confident 

 than before that the Bletchley Boring, if it did not actually touch 

 the Palaeozoic floor, came extremely near to it ; and we may safely 

 assign to it a level a little deeper than — 150, 3 which is practically 

 identical with that at Calvert. We may also infer that the Palaeozoic 

 floor, in the near neighbourhood, consisted of Charnian igneous 

 rocks. 



i H. B. Woodward, ' Jurassic Bocks of Britain ' Mem. Geol. Surv. vol. iv 

 (1894) pp. 513, 515 & vol. v (1895) pp. 340, 341. 



' 2 Final Rep. Royal Comm. on Coal-Supplies, pt. ix (1905) p. 25. 



3 According to the engineer's record, the well started about +260 feet, and 

 the boring went to a depth of 410 feet. In the Royal Commission's Report, 

 and in ' Jurassic Rocks of Britain ' Mem. Geol. Surv. vol. v (1895) p. 48, the 

 depth is given as 419 feet. The former figure has been taken. 



