[ 454 ] 
*hnent, by which alfo the fpecific weight of the 
Diamond came out lefs than Mr. Elhcot’s , yet it may 
well be queftion’d, whether Sir Ifaac had, at the time 
when he made his trials, cither fo many or fo per- 
fed and weighty hones, as a favourable opportunity 
offered to this laft gentleman. I fhall therefore 
only obferve, that, admitting this laft to be the true 
fpecific weight of the Diamond, the refradive power 
of the fame, in proportion to its denfity, fhould in 
Sir Ifaac Newtons table be leftened from 14*556 to 
1 407 1 ; which would ftill be greater than what is 
found in any other body ; but is upon the whole 
more conformable to the general law of that table. 
Sir Ifaac Newton conjedured a Diamond to be 
an unduous fubftance coagulated, and found it to 
have its refradive power nearly in the fame propor- 
tion to its denfity as thofe of Camphire, Oyl-Olive, 
Lintfeed Oyl, Spirit of Turpentine and Amber, 
which are fat fulphureous utiduous bodies : all which 
have their refradive powers two or three times 
greater in refped to their denfities than the refrac- 
tive powers of other fubftances in refped of theirs. 
Yet muft it be allowed that a Diamond fuffers no 
change by heat in any degree, contrary to the known 
property of Sulphurs j and as it is moft reafonable 
in our Philofophy to treat fuch bodies as ftmplc, 
in which we are not able to produce any change or 
reparation of parts, we muft therefore on that account 
confider a Diamond as a ftmple body and of tkc 
Chryftalline kind. 
Glafs, which is a faditious concrete of Sand and 
Alkaline Salt, is nearly found to aflume the mean 
gravity of Stones and Chryftals. 
If, 
