PHYSICAL sNp LITERARY. 93 
parts, upon account of their minutenefs, 
lofe their powers of refraction as well as 
reflexion? And to what known property 
of light or bodies can this be attribu- 
ted? 
QUEER. XXII. Ir the fits are produced 
by an alternate acceleration and retarda~ 
tion of the particles of light, fome of the 
particles, which are fwift enough to be 
tranfmitted at the firft furface ofa tranf- 
parent. medium, muft overcome the re- 
flecting power more eafily than others ; 
namely, thofe that happen to be in their 
point of greateft celerity or neareft to phar 
Now, muft not rays that are moving with 
different velocities, be differently bent from 
their courie, as we argued above with re- 
{pect to fimple coloured rays, by the fame 
refractive power? Why theretore is not 
every beam of light, homogeneal or he- 
terogeneal, diffufed by refraGtion into in- 
numerable rays, according to the refpec- 
tive velocities with which they entered 
the refracting furface? Is it a fufficient 
an{wer to this query, That rays which are 
farchen from thei eir point of greateft {wift- 
5) nels 
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