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no experiments can more clearly shew, noj: only the 
general fact of an attraction exerted by bodies upon 
the entire beam of light, but also upon the individual 
colorific rays, of which that beam is composed ; for 
when one species of matter is thus drawn out of its 
course by another, in what language can we express 
the fact, if we do not call it attraction ? How, then, 
must we suppose this attraction to be exerted ? 
485. " Have not the small particles of bodies cer- 
tain powerSj virtues or forces," says Newton, " by 
which they act at a distance, not only upon the rays 
of light for reflecting, refracting, and inflecting them, 
but also upon one another, for producing a great 
part of the phenomena of nature ? For it is well 
known that bodies act one upon another by the at- 
tractions of gravity, magnetism and electricity." 
" How these attractions maybe performed/' he con- 
tinues, " Ido not here consider. What I call attraction, 
may be performed by impulse, or by some other means 
unknown to me. I use that word here to signify 
only, in general, any force by which bodies tend to- 
wards one another, whatsoever be the cause. For 
we must learn, from the phenomena of nature, what 
bodies attract one another, and what are the laws 
and properties of the attraction, before we inquire the 
cause by which the attraction is performed. The at- 
tractions of gravity, magnetism, and electricity, reach 
to very sensible distances, and so have been observed 
by vulgar eyes ; and there may be others which 
reach to so small distances, as hitherto escape obser- 
vation ; and perhaps," he adds, " electrical attraction 
may reach to such small distances, even without 
o 
