** On the ground abroad this firestone will not succeed for
pavements, because, probably, some degree 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, ferments strongly in mineral acids. Though the
white stone will not bear wet, yet in every quarry at intervals 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 this 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.
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