8 NATURAL HISTORY 
them frequently on that fteep, juft under the foil, in the chalk, and 
of a confiderable fize. In the lane above Well-bead, in the way 
to EmJJ^ot, they abound in the bank in a darkifh fort of marl; 
and are ufually very fmall and foft : but in Clays Pond, a little far- 
ther on, at the end of the pit, where the foil is dug out for ma- 
nure, I have occafionally obferved them of large dimenfions, per- 
haps fourteen or fixteen inches in diameter. But as thefe did not 
confift of firm ftone, but were formed of a kind of terra lapldofi, 
or hardened clay, as foon as they were expofed to the rains and 
froft they mouldered away. Thefe feemed as if they were a very 
recent produftion. In the chalk-pit, at the north-weft end of 
Hanger, large naut'tll are fometimes obferved. 
Ir| the very thickeft ftrata of our freefone, and at coniiderablc 
deptlis, well-diggers often find large fcallops or peEilnes, having 
both fliells deeply ftriated, and ridged and furrowed alternately. 
They are highly impregnated with, if not wholly compofed of, 
the ftone of the quarry. 
LETTER IV. 
TO THE SAME. 
A s in a former letter the freejlone of this place has been only 
mentioned incidentally, 1 flhall here become more particular. 
This ftone is in great requeft for hearth-ftones, and the beds 
of ovens: and in lining of lime-kilns it turns to good account ; 
for the workmen ufe fandy loam inftead of mortar ; the fand of 
which fluxes, ^ and runs by the intenfe heat, and fo cafes over the 
^ There may probably be alfo in the chalk itfelf that is burnt for lime a proportion of 
fand ; for few chalks are fo pure as to have none. 
whole 
