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matter, as can be fuppofed to be contained in any 
Tingle emiffion of light, 95100 times in every fecond, 
no fenfible alterations in the fyffem could take place 
in millions of years. And perhaps light does not 
iffue from the fun To frequently as 95100 times in 
a fecond. 
P. S. The late Dr. Pemberton, of Grefham Col- 
lege, to whom the foregoing paper was communi- 
cated, about twelve months before his death, in a 
letter with which he favoured the authour, upon the 
fubjecf, remarked, that he had no material obje&ion 
to any part of the reafoning, except it was, that the 
particles of light are too peremptorily fpoken of as 
fpherules. Their real figure is quite unknown j but 
the probability is, that they are not lpherical, fince 
Sir Ifaac Newton found that their different tides have 
different properties. As the like objection may oc- 
cur to others, it may not be improper to add a few 
words to obviate it. I would by no means be under- 
Hood to affert, that the particles of light are of a 
lpherical figure. But, whatever their figure may be, 
1 conceive that their fize muff be fo lmall, that the 
diagonal of each little folid cannot exceed one 
millionth of one millionth of an inch, or, at leaff, 
2 that 
June 13, 1770. 
s. 
