THE GENESIS OF TEE LAW OF GRAVITY 337 



is that a sphere attracts all outside bodies as if its mass were concen- 

 trated at its center. 



Thus he reached his goal at last, and after twenty years of work, 

 ranging over many subjects, the key of the universe lies in Newton's 

 hand. Surely, now, he will publish it and proclaim its discovery to 

 the world. Not so; he must first have the joy of undisturbed posses- 

 sion. Also there is much more to be done. The law he has proved 

 is an " open sesame " to wider knowledge. Or, to change the figure, 

 it is as if a mountain climber, who has toiled upward and upward, now 

 stands at last on the topmost height. As he is climbing he thinks that 

 if he can but gain the summit it will be enough — he will be content 

 and rest. The toiling climber does not realize what awaits him at the 

 top, until the whole panorama of plain and mountain, of crag and 

 canyon, bursts upon his astonished sight. With this before him he 

 forgets his toil, forgets to rest and devours the view. So with Newton, 

 having at last mastered the central law upon which the universe swings, 

 he saw the members of the solar system sweeping in orderly grandure 

 through space, he saw this law governing every motion of every satellite 

 and comet, accounting for the nutations and perturbations, which be- 

 fore seemed to make order impossible. He saw it causing the tides 

 with the rising and setting of the sun and moon. All this and more 

 he saw, and we can not wonder that instead of rushing into print, he 

 shut himself up and worked and thought and wrote, and calculated 

 and worked and thought and wrote. 



For two years he labored, sleeping little, eating little, always lost 

 in thought. Often, it is said, on rising, he would sit for hours half 

 dressed upon his bedside. Often for days, he would seem oblivious 

 to all external events. The following story well illustrates his abstrac- 

 tion. One day a friend, Dr. Stukely, called and found Newton's 

 solitary dinner ready on the table. After waiting a long while, Dr. 

 Stukely thought to play a joke on Newton, which he proceeded to do 

 by eating his dinner for him. Having done so, he rearranged the table, 

 covering the dishes so that it would not appear that anything had 

 happened. At length Newton appeared, and, after greeting his friend, 

 sat down to dinner, but, on lifting the cover, said in surprise, " Dear 

 me ! I thought I had not dined, but I see I have." 



So it went on for two full years, until Newton felt that his work 

 was done. He divided it into three books. The first is entitled The 

 Mathematical Principles of Natural Philosophy, and comprises about 

 two hundred and fifty pages. It reminds one of a geometry, with its 

 propositions, theorems, scholiums and problems. The first book is 

 divided into fourteen sections and contains ninety-seven propositions, 

 fifty theorems and forty-seven problems. Book II. discusses The 

 Motions of Bodies. Here are found fifty-three propositions, forty-one 



