10 
THE NATURAL HISTORY 
[LETT. 
the rain tears the slabs to pieces.^ Thongli this stone is too 
hard to be acted on by vinegar, yet both the white part and 
even the blue rag ferment strongly in mineral acids. Though 
the white stone will not bear wet, yet in every quarry at in- 
tervals there are thin strata of blue rag, which resist rain and 
frost, and are excellent for pitching of stables, paths, and courts, 
and for building of dry walls against banks; a valuable species 
of fencing, much in use in tliis village ; and for mending of 
roads. This rag is rugged and stubborn, and will not hew to a 
smooth face ; but is very durable : yet, as these strata are 
shallow and lie deep, large quantities cannot be procured but at 
considerable expense. Among the blue rags turn up some blocks 
tinged with a stain of yellow or rust colour, which seem to be 
nearly as lasting as the blue ; and every now and then balls of 
a friable substance, like rust of iron, called rust balls. 
In Wolmer Forest, I see but one sort of stone, called by the 
workmen sand or forest-stone. This is generally of the colour of 
rusty iron, and might probably be worked as iron ore ; is very 
hard and heavy, and of a firm, compact texture, and composed 
of a small roundish crystalline ^rit, cemented together by a 
brown, terrene, ferruginous matter ; will not cut without difficulty, 
nor easily strike lire with steel. Being often found in broad flat 
pieces, it makes good pavement for paths about houses, never 
becoming slippery in frost or rain ; is excellent for dry walls, and 
is sometimes used in buildings. In many parts of that waste it 
lies scattered on the surface of the ground, but is dug on Weaver's 
Down, a vast hill on the eastern verge of that forest, where the pits 
are shallow and the stratum thin. This stone is imperishable. 
From a notion of rendering their work the more elegant, and 
giving it a finish, masons chip tins stone into small Iragments 
about the size of the head of a laige nail, and then stick the 
pieces into the wet mortar along the joints of their freestone 
walls : this embellishment caiTies an odd appearance, and has 
occasioned strangers sometimes to ask us pleasantly " whether 
we fastened our walls together with tenpenny nails." 
^ " Firestone is full of salts, and has no sulphur : it must be close grained, 
and have no interstices. Nothing supports fire like salts ; saltstone perishes 
when exposed to wet and frost." — Plot's Staff, p. 152. 
