^ 7 ? ) 
Diamond, and aftervvai;ds fays, that feme Diamonds 
wou’dj and iomc wou'd not Qdno in the Dark: But if 
any one elfe has fince then made a Difeovery, that all 
Diamonds wou’d give Light in the Dark, they have been 
very unkind to -the World in not letting them know k, 
becaufe Pm well affur’d that a great many People have 
• been but too often cheated with ’em, which I hope to 
prevent for the future 5 hut thus much I muft take leave to 
lay, that I never underftood any fuch thing till I difeo- 
ver’d it my felf, tho’ now I remember, that Mr. 
veral times fpoke tome of Mr. Claytons Diamond, lament- 
ing that he cou’d not prevail with the Owner to part 
with it at any rate. I have now by me a yellow Dia- 
mond, which I have (heWn to a great many Jewellers 
and others,, and but a very fewof em will allow it to be 
a Diamond 5 but by as many Tryals as I have made, I 
think my way of diftinguiOiing Diamonds is fo certain, 
that none need fear to affirm ’em to be fo, even upon 
Oath. ' . , 
A Diamond, byan eafie flight fridion in the Dark, with 
any foft Animal Subftance, as the Finger, Woollen, Silk, 
appears in its whole Body to be Luminous 5 nay, if 
you keep rubbing for a little while, and then expofe it 
to the Eye, ’twill remain fo for fome little time : But if 
the Sun be 18 Degrees below the Horizon, if any one 
holds up a piece of Bays or Flannel ftretch’d tight be- 
tween both hands, at fome diftance from the Eye, and 
another rubs the Bays or Flannel with a Diamond fwiftly 
and pretty hard on the other fide of it, the Light to the 
Eye of him that holds it, feems much more pleafant and 
perfed than any other way I have yet try’d. But what 
to me feems more furprizing than all I have mention’d, 
is, that a Diamond being expos’d to the open Air in view 
of the Sky, gives almoft the fame Light of it felf with- 
^ rubbing, as if rabb’d in a dark Room ^ and if in the 
L open 
