33° Dr, withering on the 
ing has been made in order to get materials for mending the- 
roads, the rock appears to be compofed of mafles of irregular 
rhomboidal figures : fome of thefe mafles inclofe rounded peb- 
bles of the fame materials. At the diftance of four, five, or 
fix miles from the hills, as at Billion, Willenhall, and Wed- 
nefbury, the Rag-ftone is frequently found fome feet below 
the fur face in rhomboidal pieces, forming an horizontal bed 
of no great depth, and feldom of more than a few yards ex- 
tent. Over the whole of this tradl of country it is ufed to 
mend the roads, arid lately has been carried to Birmingham to 
pave the ftreets. Some people fell it in powder, as a fubftitute 
for emery in cutting and polifhing. 
MORE OBVIOUS PROPERTIES. 
Its appearance dark grey, with numerous minute fhinlng 
cryftals. When expofed to the weather gets an ochry colour 
on the outride ; ft r ikes fire with fteel ; cuts glafs ; melts, 
though not earily, under the blow-pipe. Heated in an open 
fire becomes magnetic, and lofes about 3 in 100 of its weight. 
EXPERIMENT S* 
A. After three drams had been broken to fmallpieces with a 
hard fteel hammer, upon a plate of the fame metal, it was 
ground to an impalpable powder in one of Mr. wedgewood’s 
China mortars. I he mortar, which had been previoufly 
weighed, loft only one-third of a grain weight during this 
operation. 
B. This pow^der was repeatedly wafhed with pure water, fo 
as to carry oft all the finer parts, and the coarfer ground again, 
until 
