( 6i 8 ) 
and n be tinged with a bluilh Colour, and all be- 
tween o and B of a bright White. 
TOSTSCRITT. 
T HE Bending of Rays of Light juft as they 
come to be reflected or refra&ed, may be 
eafily underftood by fuch as are well acquainted with 
thole Properties of Light, which Sir Ifaac Newton 
calls their Fits of eafy Reflection , and Fits of eajy 
Tranfmijflon ; without any Hypothefis, but by Con- 
sequences fairly drawn from Experiments and Ob- 
fervations. But as Signior Rizzetti does not feem 
C in his Book ) to have the leaft Notion of thofe 
Properties of Light, and the nice Obfervations on 
which they are founded ; and feveral other Perfons 
have not Time to read thofe Parts of the Opticks 
with fufficient Application ; to Ihew how the fame 
Power of the Surface of a denfe Medium may both 
attra<ft and repel under different Circumftances 
I content myfelf here with giving the Hypothefis, 
which Sir Ifaac does before he comes to that Part 
of his Book where he demonftrates the Fits above- 
mentioned. 
If G G be the Surface of a denfe Medium 
GDDG, on which a Tremor is cauled by the 
Warmth communicated to it by the Rays of Light, 
fo as to give a Wave-like Motion to the Medium 
immediately next to the Surface G G ; as that vi- 
bratory Motion is performed, the Medium alter- 
nately pulhes from the Surface, and returns towards 
it (as is reprefented by the Pofirion of the Darts in 
the 
