Geology of Cambridgeshire. 245 



result of his observations to me. Mine were principally made at 

 the pit on Gogmagog hills ; and as the contents of the two pits 

 seem to differ in some respects, I have great pleasure in subjoining 

 his remarks in the same terms as they were conveyed to me. His 

 conjectures as to the cause of these alluvial deposits, will be read 

 •with great interest by Geologists* 



*' The hill at Harston is of a conical form, and situated about a 

 quarter of a mile S. E. of the village, and about five miles S. W. of 

 Cambridge. I selected from the rubble which is deposited on the 

 summit of the hill the following specimens. 



1. Rounded pebbles of very hard chalk, scarcely softer than the 



Antrim limestone. These compose three-fourths of the mass 

 of the rubble. 



2. Angular masses of striped flint. These are numerous and very 



large; one cylindrical piece that I measured being one-third 

 of a foot in diameter and one foot long, 



3. Fragments of septaria. 



4. Fragments of a shelly limestone. 



5. Ochreous balls, resulting probably from the decomposition of 



pyritous nodules. 



6. Angular or scarcely rounded pebbles of trap or greenstone. 



7. Organic remains, viz. 



a small fusiform belemnite ; 



a large belemnite ; 



a small gryphite ; 



a large oyster ; vide fig. 7 & 8. PI. 8. Townshend j 



some bones and teeth. 



