C 999 ) 
of Light are retarded in paffing thofe Diaphanous Bo 
dies ; and thereby fo naturally explicating the Laws of 
Refra&ion ? 
4. Suppofing Light to be propagated in a Wave, 
how it comes to pais that this Propagation being either 
retarded or accelerated in a Diaphanous Body,asGlafs,@V. 
does, upon its going out of that Medium, acquire again 
the fame degree of Velocity it had before it came on, 
there being no new impulfe or impediment to alter th$ 
Velocity it had in the other Medium ? 
. 5*. Why Mercury being fo pure, fimple and homoge- 
neous a Fluid, is almoft the only one that is not tranf* 
parent ? 
6. Whether the Reflexion of Light on the Surfaces of 
Glafs, Water, and the Shade of the moft perfect Pellu- 
cid being always very difcernable, be not Arguments 
that the Beams pafs their Media with more difficulty 
than they do the Air > 
7. Whether any Texture of Atoms of the fame ma- 
teria Prima can be fuppofed to anfwer to the Phenomena 
of the Pellucidity of heavy and Opacity of light Bodies ? 
8. Whether, if light (as it is moft likely) be a Tre- 
mour, Shake, or Undulation of the ^ther, as Sound is 
of the Air ; and if the iEther do confift of fo rarified 
Parts, as to penetrate all Bodies with full liberty, as is 
generally fuppofed ; moft if not all Bodies ought not to 
be tranfparent ? 
9. Whether the Matter of the Univerfe be not of fi> 
veral Kinds in Minimis , and not conftituted by the va- 
rious Texture and Coalition of the fame fort of Atoms, 
as it has been held by the Epicurean and Atomical Phi* 
Iofophers ) which at prefent obtain in the World. 
ft r r i 
I That* 
