a vast multitude of oval-figured animalcula, to the number of 6,000 or 8,000 in a single drop.-Transactions of the Royal Society.

NEWTON

SIR ISAAC NEWTON was born at Woolstrop, Lincolnshire, England, Dec. 25, 1642 (O. S.). His father, a farmer of good descent, had died before he was born. He attended the free grammar school at Grantham, but left early. His ability in making mechanical toys, however, brought his mother to return him to school, and later send him to Cambridge. He took his degree in 1665, in 1667 was made a fellow of the university, and in 1669 professor of mathematics. He had already discovered his method of fluxions, which closely resembles Leibnitz's Differential Calculus, invented about the same time.

In 1672 he was elected a member of the Royal Society and soon afterwards sent to them his communication concerning how he had broken up light by means of a prism, thus showing the compound nature of the sun's rays.

In 1682 a new measurement of the meridian was brought to his notice. Sixteen years before he had conceived the idea of universal gravity and had calculated the pull the earth would exert on the moon in accordance with its supposed mass. The result had not agreed with the speed of revolution of the moon and Newton had laid the hypothesis aside. He saw that the new calculation of the size of the earth was in the right direction and set to work at a re-calculation of the problem. The solution is given below.

When he saw that the hypothesis of a universal attraction between masses was coming close to agreeing with the known facts, he was so agitated that he had to ask a friend to complete it for him.

Some years later he began to investigate chemistry, but the story is that his papers were destroyed by his dog and he never quite recovered from the shock. From 1695 to 1699 he was warden of the mint, and from 1699 to his death master of the mint, a place paying from $6,000 to $9,000 a year.

He died March 20, 1727. His discoveries in light, in gravitation,

including the universal theory and its application to the planets and the tides, or in mathematics would any one of them make his name deserving of immortality.

THE DIFFUSION OF LIGHT

A letter of Mr. Isaac Newton, Professor of Mathematics in the University of Cambridge; containing his new theory of Light and Colours; sent by the Author to the Editor from Cambridge, Feb. 6, 1671-3; to be communicated to the Royal Society. No. 80, p. 3,075.

SIR-To perform my late promise to you, I shall without further ceremony acquaint you that in the beginning of the year 1666 (at which time I applied myself to the grinding of optic glasses of other figures than spherical,) I procured a triangular glass prism, to try therewith the celebrated phenomena of colours. And for that purpose, having darkened my chamber, and made a small hole in my window shuts, to let in a convenient quantity of the sun's light, I placed my prism at this entrance, that it might be thereby refracted to the opposite wall. It was at first a very pleasing diversion to view the vivid and intense colours produced thereby; but after a while applying myself more circumspectly, I was surprised to see them in an oblong form; which according to the received laws of refraction, I expected would have been circular. They were terminated at the sides with straight lines, but at the ends the decay of light was so gradual, that it was difficult to determine justly what was their figure; yet they seemed semicircular.

Comparing the length of this coloured spectrum with its breadth, I found it about five times greater; a disproportion so extravagant, that it excited me to a more than ordinary curiosity of examining from whence it might proceed. I could scarce think that the various thickness of the glass, or the termination with shadow or darkness, could have any influence on light to produce such an effect; yet I thought it not amiss, first to examine those circumstances, and so tried what would happen by transmitting light through parts of the glass of divers thicknesses, or through holes in the window of divers sizes, or by setting the prism without, so that the light might pass through it, and be refracted before it was terminated by the hole; but I found none of these circumstances material. The fashion of the colours was in all these cases the same.