ewton took his degree of Bachelor of Arts at Cambridge, in January, in the year Sixteen Hundred Sixty-five. The faculty of Trinity would not even consider his leaving the college: he was as valuable to them as he would be now if he were a famous football-player. Besides the scholarship, there were ways provided so he could earn money by private tutoring and giving lectures in the absence of the professors.
He had written his essay on fluxions, described their application to fluents and tangents, and devised a plan for finding the radius of curvity in crooked lines. In August of the same year that Newton was given his degree, the college was dismissed on account of an epidemic, and Newton went home to Woolsthorpe to kill time. In September, Sixteen Hundred Sixty-five, he then being twenty-three, while seated in his mother's garden, Newton saw that storied apple fall. What pulled it down? Some force tugging at it, surely!
Galileo had experimented with falling bodies, and had proved that the weight and size of a falling body had nothing to do with its velocity, save as its size and shape might be affected by the friction of the atmosphere. The first person to put into print the story of the falling apple was Voltaire, whose sketch of Newton is a little classic which the world could ill afford to lose. Adam, William Tell and Isaac Newton each had his little affair with an apple, but with different results.
The falling apple suggested to Newton that there was some power in the ground that was constantly pulling things toward the center of the earth.
This power extended straight down into the earth—he knew it—he had dropped a stone into a mine, and had also dropped things from steeples. He dropped apples from kites by an ingenious device of two strings, and he concluded that an apple taken a hundred miles up in the air would return to earth.
He then began to speculate as to just what a body would do a thousand or ten thousand miles from the earth. So high as we could go, or as deep as we could dig, this drawing power was always present. The Law of Gravitation!
If a cannon-ball was fired in a straight line at a distant target, the gunner had to elevate the aim if he would hit the target, for the ball described a curve and would keep dropping to the earth until it struck the ground. Something was pulling it down: what was it? The Law of Gravitation!
The moon was attracted toward us and would surely fall into us, but for the fact that there were other attractions drawing her toward them. The movements of the planets were owing to the fact that they were obeying attractions. They were moving in curves, just like cannon-balls in motion. They had two movements, also, like the cannon-ball.
Newton had noticed that the stars within a certain territory all moved in similar directions, and so must be acted upon by the same influences. The Law of Gravitation!
It is held by many people in East Aurora and elsewhere that Newton's invention is a devilish device originated for the benefit of surgeons and crockery-dealers. But this is not wholly true.