9 8 NATURAL HISTORY 
evidence of which, we need go no farther than the rocky beach, 
and precipices at St. Michael’s Mount. Moorftone, where there is 
no defeCt, does not cleave to faces, as flat and killas, but breaks 
irregularly, as marble ; yet can the mafons cleave tall columnar 
maffes eight or ten feet long, and fometimes longer, out of a block 
of ftone : they do not depend on a hole full of water to foak and 
foften the ftone, nor to feparate it into a number of pieces at ran- 
dom m ; their way of cleaving it is this : Having pitched on a rock 
of proper fize, they line it out, and in the lines fink with a pointed 
inftrument, called a pick, feveral holes, about three inches deep, as 
many wide, and four or five inches long. Having prepared thefe 
holes, they infert a large iron wedge, called a gad, in each hole, 
and line the wedges on each fide with a thin piece of iron plate ; 
two of the mafons then (each furnifhed with a fledge) drive the 
wedges in an equable manner, and the ftone will cleave the whole 
length defired. 
That this ftone is of the fame nature with the Oriental granite, 
is now no longer to be difputed ; by that name therefore, as better 
known, I fhall henceforth diftinguifh it, and range the feveral forts 
I have met with in Cornwall according to the feveral colours of 
their grounds : for perfpicuity fake, let the reader obferve, that in 
fuch compound ftones as this, the prevailing matter or cement of 
any ftone is called the groimd of that ftone, and the fpots, veins, 
or variegations fixed in that cement, I fhall call the charge of that 
ftone, as we might with equal propriety ( if it were not to multiply 
names) call the growid of any ftone the field of that ftone. 
Five forts of this granite I have obferved, the white, the dufky 
or dove-coloured, the yellow, the red, and the black. 
White. In the parifh of Conftantine, in the Hundred of Kerrier, there 
is great plenty of this ftone ; the ground of feveral degrees of white- 
nefs ; the whiteft of all, which is the beft, confifts (as to its ground) 
of milk-white opake, tabulated, gloffy grains of quartz, the grains 
rectangular, and ufually columnar, from the fourth of an inch and 
lefs in diameter ; the charge confifts of brown and bright filvery 
of talc, about the tenth of an inch diameter ; the ground is 
fo white, that the brown talc has the appearance of black, when it 
is near and fronts the eye ; but at a little diftance, the ground pre- 
vails fo much, that this ftone, for many years after it is wrought, 
looks abfolutely white : it is of a clofe grit, cuts well into mold- 
ings, in a moderate fire grows fomewhat whiter and more brittle, 
but without mixture will not vitrify in a ftrong fire, gives fire with 
fteel, ferments not with aqua forth : it has a very good effe& in 
Hill’s Foffils, page 499. 
building, 
