NEWTON. 
ttieasurmg tlie force of the wind blowing 
against him, by observing how much farther 
he could leap in the direction of the wind, or 
blowing on his back, than he could leap the 
contrary way, or opposed to the wind; an 
early mark of his original infantine genius. 
After a few years spent here, his mother 
took him home ; intending, as she had no 
otlier child, to have the pleasure of his com- 
pany ; and that, after the manner of his fa- 
ther before him, he should occupy his own 
estate. 
But instead of attending to the markets, 
or the business of the farm, he was always 
studying and poring over his books, even by 
stealth, from his mother’s knowledge. On 
one of these occasions his uncle discovered 
him one day in a hay-loft at Grantham, 
whither he had been sent to the market, 
working a mathematical problem ; and hav- 
ing otherwise observed the boy’s mind to 
be uncommonly bent upon learning, he 
prevailed upon his sister to part with him ; 
and he was accordingly sent, in 1660, to 
Trinity College, in Canrbridge, where his 
uncle, having himself been a member of it, 
had still many friends. Isaac was soon 
taken notice of by Hr. Barrow, who was 
at this time appointed the first Lucasian 
professor of mathematics ; and observing 
his bright genius, contracted a great friend- 
ship for him. At his commencement, Euclid 
was first put into his hands, as usual ; but 
that author was soon dismissed, seeming to 
him too plain and easy, and unworthy of 
taking up his time. He understood him 
almost before he read him ; and a cast of his 
eye upon the contents of his theorems, was 
sufficient to make him master of them : and 
as the analytical method of Des Cartes was 
then much in vogue, he particularly applied 
to it, and Kepler’s optics, cSsc. making several 
improvements on them, which he entered 
upon the margins of the books as he went 
on, as his custom was in studying any au- 
thor. 
Thus he was employed till the year 1664, 
when he opened a way into his new method 
of Fluxions and Infinite Series ; and the 
same year took the degree of Bachelor of 
Arts. In the mean time observing, that the 
mathematicians were much engaged in the 
business of improving telescopes, by grind- 
ing glasses into one of the figures made by 
the tliree sections of a cone, upon the prin- 
ciples then generally entertained, tliat light 
was homogeneous, he set himself to grinding 
of optic glasses, of other figures than sphe- 
rical, having as yet no distrust of the ho- 
mogenous nature of light; but not hitting 
presently upon pny thing in this attempt to 
satisfy his mind, he procured a glass prism, 
that he might try the celebrated phenomena 
of colours, discovered by Grimaldi not long 
before. He was much pleased at first with 
the vivid brightness of the colours produced 
by this experiment ; but after a while, con- 
•sidering them in a philosophical way, with 
that circumspection which was natural to 
him, he was surprised to see them in an 
oblong form, which, according to the re- 
ceived rule of refractions, ought to be cir- 
cular. At first he thought the irregularity 
might possibly be no more than accidental ; 
but this was what he could not leave with- 
out further enquiry : accordingly he soon 
invented an infallible method of deciding 
the question, and the result was his New 
Theory of Light and Colours. 
However, the theory alone, unexpected 
and surprising as it was, did not satisfy him ; 
he rather considered the proper use that 
might be made of it for improving teles- 
copes, which was his first design. To this 
end, having now discovered that light was 
not homogeneous, but an heterogeneous 
mixture of differently refrangible rays, he 
computed the errors arising from this dif- 
ferent refrangibility ; and, finding them to 
exceed some hundreds of times those occa- 
sioned by the circular figure of the glasses, 
he threw aside his glass works, and began to 
consider the subject with precision. He was 
now sensible that optical instruments might 
be brought to any degree of perfection de- 
sired, in case there could be found a reflect- 
ing substance which could polish as finely as 
glass, and reflect as much liglit as glass 
transmits, and the art of giving it a parabo- 
lical figure he also attained ; but these at first 
seemed to him very great difficulties; nay, 
he thought them almost insuperable, when 
he further considered, that every irregula- 
rity in a reflecting superficies makes the 
rays stiay five or six times more from their 
due course, than the like irregularities in a 
refracting one. 
Amidst these speculations, he was forced 
from Cambridge, in 1665, by the plague ; 
and it was more than two years before he 
made any further progress in the subjeef. 
However, he was far frou) passing his time 
iilly in the country ; on the contrary, it was 
here, at this time, tliat he first started the 
hint that gave rise to the system of the 
world, which is the main subject of the 
Principia. In his retirement he was sitting 
alone ill a garden, when some apples falling 
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