8 THE NATURAL HISTORY [LETT. 



one into the other, the alternate flutings or grooves, and the 

 curved form of my specimen are much easier expressed by the 

 pencil than by words. 



Cornua Ammonis are very common about this village. As 

 we were cutting an inclining path up the Hanger, the labourers 

 found them frequently on that steep, just under the soil, in the 

 chalk, and of a considerable size. In the lane above Well-head, 

 in the way to Emshot, they abound in the bank, in a darkish 

 sort of marl, and are usually very small and soft : but in Clay's 

 Pond, a little farther on, at the end of the pit, where the soil is 

 dug out for manure, I have occasionally observed them of large 

 dimensions, perhaps fourteen or sixteen inches in diameter. 

 But as these did not consist of firm stone, but were formed of 

 a kind of terra lapidosa, or hardened clay, as soon as they were 

 exposed to the rains and frost they mouldered away. These 

 seemed as if they were of very recent production. In the 

 chalk-pit, at the north-west end of the Hanger, large nautili 

 are sometimes observed. 



In the very thickest strata of our freestone, and at con- 

 siderable depths, well-diggers often find large scallops orpectines, 

 having both shells deeply striated, and ridged and furrowed 

 alternately. They are highly impregnated with, if not wholly 

 composed of, the stone of the quarry. 



LETTER IV. 



TO THOMAS PENNANT, ESQ. 



As in a former letter the freestone of this place has been only 

 mentioned incidentally, I shall here become more particular. 

 This stone is in great request for hearthstones and the beds 

 of ovens ; and in lining of lime-kilns it turns to good account ; 

 for the workmen use sandy loam instead of mortar ; the sand of 

 which fluxes, and runs by the intense heat, and so cases over 

 the whole face of the kiln with a strong vitrified coat like glass, 

 that it is well preserved from injuries of weather, and endures 



