98 Mr. H. Seeley on Cambridge Geology : — 



turally supposed to be an outlier of the Shanklin Sands ; and so 

 it continued to be regarded until Mr. Barrett discovered that it 

 was really a member of the Oolitic series. On what grounds it 

 was determined to be the particular rock mentioned, or Calca- 

 reous Grit at all, I am not aware, unless, indeed, it were from 

 Dr. Wright's speculation that Lower Calcareous Grit had a pro- 

 bable existence in this district ; nor have I learnt why the clay 

 above was mapped as Kimmeridge Clay. Some fossils were 

 collected and placed in the Woodwardian Museum. So remark- 

 able was the assemblage, and in some respects so unlike what 

 would have been anticipated, that, after a careful examination of 

 the specimens, I could not but suspect that, in the haste with 

 which the north-west corner had been mapped, something must 

 have been wrongly interpreted. Accordingly, at the first oppor- 

 tunity, I established myself in the village of Elsworth, and pro- 

 ceeded to investigate the nature and relations of the rock on 

 which it stands. 



Elsworth is four miles and a half due south of St. Ives — the 

 well-known locality for Oxford Clay, — nearly the same distance 

 due north of Bourn, and about eight miles W.N.W. of Cam- 

 bridge. The country about is, on a small scale, quite hill and 

 valley, the village of Elsworth itself being built in a rather deep 

 hollow. The hills are mostly of boulder clay, while the valleys 

 produced by its denudation often expose the stratified beds be- 

 neath. A brook runs through the village, and ultimately finds 

 its way into the Ouse. 



As the streamlet flows between the principal rows of houses, 

 its banks were naturally the first places examined ; and here and 

 there along them was seen peeping out a reddish-brown calca- 

 reous rock, highly charged with iron-shot oolitic particles, and 

 very hard, but readily separating by cracks into small pieces. It 

 extends throughout the length of the village, and at its southern 

 end dips under a hill of dark-blue stratified clay ; to the north 

 it is denuded : this is the nearest approach to a section to be 

 seen. I wished, however, to see the rock where it had not been 

 weathered, as also to obtain fossils from the clay above ; and so 

 the Rev. H. Dobson, the rector, kindly granted permission to 

 sink the necessary pits through the rock. The first attempt was 

 a failure ; for, though a very promising site was selected within 

 four yards of an exposure by the roadside, it was found, after a 

 large excavation had been made, that the whole deposit was 

 bouldercd away. The next trial was more successful ; and, sin- 

 gularly, though in the immediate vicinity of the other, there was 

 no trace whatever of the drift clay. We sunk through six feet 

 and a half of a dark-blue laminated clay, which here and there 

 contained a layer, of chocolate- or ferruginous colour, abounding 



