[ *9 ] 
both of the dove-coloured Cornifh granite, difcoloured 
as it feems by fire. But the ancients feem not to 
have made their weights of ftone by choice, but for 
want of metal ; for they could not be ignorant, that 
lead, brafs, or iron, was more compact, ponderous, 
and durable : and that flone was liable to become 
* f 
heavier, by alfuming into its fubftance the moifture 
and weight of adjacent bodies, and on the other 
hand to be corroded, arid become more porous and 
lighter, by means of any penetrating acid, or heat 
or drought ; and fo either exceed or fall fhort of the 
intended ftandard. Thefe inconveniences of ftone 
weights the ancients, I fay, could not but forefee ; 
they are alterations which the materials could hardly 
efcape : and therefore I conjecture, that the weights 
before us have varied : they both exceed the number 
of Roman pounds, which they were probably at firft 
adjufted to. The great weight indeed has been in- 
creafed but a fmall matter, viz. 337 grains more than 
18 pounds ; the fmall one more in proportion, viz, 
14,06 grains more than 5 pounds, i. e. above a quarter 
of a pound : nor is it to be wondered at, that, tho’ 
both of the fame fort of ftone, they ftiould have 
acquired different quantities of weight ; for the addi- 
tion muff have been according to the nature of the 
rubbifti in which they have lain. If there were any 
metallic ores (iron, for inftance, copper, or tin) or 
impregnated waters, in the rubbifh, where thefe 
jftones were depofited, then the addition would be 
great, otherwife the addition would be no more than 
that of common moifture or earth. 
Fig. 6 . is part of a vafe or bowl, fometimes made 
of brafs, or richer metal, but here of ftone, This, 
D 2 I ap- 
