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THE NATURAL HISTORY OF SELBORNE.. : 7 
were formed of a kind of hardened clay; as soon as they were 
exposed to the rains and frosts they mouldered away. These 
seemed as if they were a very recent production. 
In the very thickest strata of our freestone, and at con- 
siderable depths, well-diggers often find large scallops, having 
both shells deeply striated, and ridged and furrrowed alternately. 
‘They are highly impregnated with, if not wholly composed of, 
the stone of the quarry. 
LETTER IV. 
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 hearth-stones 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 thirty or forty years. When chiselled smooth, it 
makes elegant fronts for houses, equal in color and grain to 
the Bath stone ; and superior in one respect, that, when sea- 
soned, it does not scale. Decent chimney-pieces are worked 
from it of much closer and finer grain than Portland; and 
rooms are floored with it; but it proves rather too soft for this 
purpose. It is a freestone, cutting in all directions; yet has 
something of a grain parallel with the horizon, and therefore 
should not be surbedded, but laid in the same position that it 
grows in the quarry. On the ground abroad this firestone 
will not succeed for pavements, because, probably, some degrees 
of saltness prevailing within it, the rain tears the slabs to 
pieces. Though this stone is too hard to be acted on by 
vinegar, yet both the white part, and even the blue rag, ferment 
