What Newton accomplished in optics and in mathematics would entitle him to high rank in the world of science. Of his work in mathematics the German scholar, Leibnitz, said, "Taking mathematics from the beginning of the world to the time when Newton lived, what he had done was much the better half."
The work included in the "Principia" was most of it done between 1680 and 1686. By far the greater part was done during the last two years of this short period, or between the forty-second and forty-fourth years of his age. This work, in its scope, in its far-reaching importance, and in the order of mind required for its accomplishment, raises Newton not merely to the first rank of the world's great minds, but compels the world to admit no second in his class. His genius shone resplendent even in his own day. We have already quoted Leibnitz. A French admirer wrote to an English correspondent, "Does Mr. Newton eat, drink, sleep like other men? I picture him to myself as a celestial genius, entirely removed from the restrictions of ordinary matter." Says Lagrange (1736-1813), a great French mathematician, "Newton was the greatest genius that ever existed, and the most fortunate, for we can not find more than once a system of the world to establish." The English writer, Whewell (1794-1866), writes, "The (Law of Gravitation) is indisputably and incomparably the greatest scientific discovery ever made, whether we look at the advance which it involved, the extent of truth disclosed, or the fundamental and satisfactory nature of this truth." Pope in a striking epigram expresses the same thought:
Nature and Nature's laws lay hid in night;
God said, Let Newton be, and all was light.
La Place, who did much work along the lines laid down by Newton, says of the "Principia": "The universality and generality of the discoveries it contains, the number of profound and original views respecting the system of the universe it presents, and all presented with so much elegance, will insure to it a lasting preeminence over all other productions of the human mind."
Sir Oliver Lodge says of Newton: "In science the impression he makes upon me is only expressed by the words 'inspired,' 'superhuman.'"
Of his own work Newton says: "I know not what the world will think of my labors, but to myself it seems that I have been but as a child playing on the seashore; now finding some pebble rather more polished, and now some shell rather more agreeably variegated than another, while the immense ocean of truth extended itself unexplored before me." When asked how he made his discoveries, he replied: "By always thinking unto them. I keep the subject constantly before me, and