C 80s ) 
Refleftions brought into my mind, how vivid the fefleftive 
power of {bmt Fluids is in comparifon of that of the genera- 
lity of Solid bodies, of whicJi there is fcarce any , if there be 
any at all, that is obferved to have a ftronger Reflexi- 
on than clean ^uickftlver \ and yet (to add that upon Exp.xv. 
the by) I havefoiiietimesfound,that this it felf may be 
increafed by the addition of a Liquor. For having obferv'd,as 
I clfewhere note, that ^kkfiher^ and Reftified Oleum Petm 
are, the former of them tiie heavieft, and the later the lighteftof 
all the vifible Bnids that are yet known to us, or at leaft to me \ 
and having alfo obferved the later of them to be confiderably 
refleftive, 1 had the euriofity to try among other things, that 
related to them, the following Experiment. SoaieCDiftill^d; 
^kkftlverht\v\g put into a fmall Viol, and held in fuch a po- 
fture,that the incidentLighc was ftrongly remitted to my Eye, 
I flowly put to it fome Petroleum.thzt being well reftified was 
very clear,and obferved, thac,as this Liquor cover'd th^ ^ick- 
Jilver^ there was at the Imaginary Plain, where they both coofi- 
ned, a brisker Refleflion than the ^uickfilver alone had given 
before ; whether this increafe of Reflexive power proceeded 
from any thing produced upon the confines of the two Bodies, 
or from fome Ethereal ^md that flip'd in there,! have above de- 
clined, and fhall now forbear, to examine : But on this occafioa 
it will not be amifs to take notice, that either the furface of the 
Air it felf, as thin and yieldinga Fluid as it is, or the furface of 
a Solid,contiguous to included Air, or fome interpofed fubtile 
matter, may reflefi the Incident beams of Light more ftrongly 
than mod men would expeft. To this purpofe I rcmember,that 
a Curious Perfon having one day brought me a couple of Ra- 
ritiesj which he told me were two pieces of a folid, but tranf- 
parent,body, that he had cafually found ; in one of which there 
was a Pearly large,round,and orient, and in the other a lefs per- 
feft one ; and haviog defired ray Opinion, whether they were 
tonfiderable enough to be prefented to the King: I, after I had 
I fufficiently view*d tliem io differing Poficions, and efpecially 
! againft the Light, asked him,whethef he were fure the included 
bodies were Pearls. To which when he anfwer*d,that his Eyes 
permitted him not to doubt of it, efpecially becaufe he knew 
of no other Gems nor Stones, that had foftrong and fine a Re- 
fleftion ; I replied, that I thought they might be only bubbles 
. SM 2 of 
