On the Elsworth Rock and associated Strata. 105 



the Gryphcea dilatata, in the clay at Elsworth, and also sparingly, 

 with the Ostrea deltoidea, in the clay to the north-east, at AVil- 

 lingham. Thus the Boxworth rock is a stratum above the 

 Elsworth rock, just as the St, Ives bed is beneath it. 



It was seen that the Elsworth beds dipped to the south ; and 

 consequently the clay in that direction will also be above them. 

 Seven miles south of Elsworth is Gamlingay; and here, in a 

 brick-yard near the bogs, I heard of a rock about a foot and a 

 half thick, seven feet below the level of the pit. From the clay 

 above were obtained single specimens of Ostrea deltoidea, Gry- 

 phaa dilatata, and Ammonites bipleop. Also, in a brick-yard at 

 the top of Tetworth Hill, the Ostrea and Gryphcea were found 

 abundantly in unexpected combination with Serpula tetragona 

 and portions of Ammonites Achilles, which occurs at Bluntisham 

 and in the bed of the Elsworth brook ; and beneath was a floor 

 of rock, covered with water at the time I was there; the rock 

 was said to be white, and 18 inches thick. Between these two 

 pits there is another; but during my short stay I failed to get 

 any characteristic fossils, except two or three Gryphcea dilatatce ; 

 from this circumstance, and as it is in a hollow, it is probable 

 that the rocks at Tetworth and Gamlingay bogs are the same, 

 and that this is the clay beneath, but at present it is impossible 

 to say so with certainty. Supposing it should be so, I should 

 be still less inclined to express an opinion as to whether this 

 Tetworth rock is the same as that of Boxworth ; though, so far 

 as the evidence goes, the natural conclusion would be that it is 

 the same. They are clearly deposits in very nearly the same 

 position, and are mutually inclined ; so that, had they extended 

 continuously, and been different beds, there ought to be a second 

 rock in the vicinity of Boxworth ; but, as this has not been met 

 with, the probabilities are strong, taken in conjunction with the 

 other circumstances, that the outcrops are both of the same 

 stratum. Above this I know of no other stone bands for a long 

 way up ; but there is another one beneath the lowest yet men- 

 tioned. 



Six miles west by south of Elsworth is St. Neots ; and a little 

 to the south of the latter place, near Eynesbury, in laying the 

 plates of the Great Northern Railway, a rock was cut down to. 

 The uppermost band, of about 8 inches, was removed : it held 

 beneath a large quantity of water, which produced the singular 

 effect of giving all the workmen who drank of it the ague. Be- 

 low this bed of stone was another of clay, and then another of 

 the rock ; but whether there were any further alternations was 

 not determined. The rock is described as having the aspect of 

 Cornbrash. In the well at Conington, 150 feet below the St. 

 Ives rock, another rock was reached, but not pierced, a small 



