It would only account for the emotionally vivacious side of this nature. There was also the other side, on which Tyndall also insists: the love of order, the extreme tenacity, the high self-discipline able to convert the fire within into a clear concentrated glow. In the fusion of these two qualities “he was a prophet,” says Tyndall, “and often wrought by an inspiration to be understood by sympathy alone.” His expansive emotional imagination became the servant of truth, and sprang into life at its touch. In carrying out physical experiments he would experience a childlike joy and his eyes sparkled. “Even to his latest days he would almost dance for joy at being shown a new experiment.” Silvanus Thompson, in his book on Faraday, insists (as Tyndall had) on the association with this childlike joy in imaginative extravagance of the perpetual impulse to test and to prove, “yet never hesitating to push to their logical conclusions the ideas suggested by experiment, however widely they might seem to lead from the accepted modes of thought.” His method was the method of the “Arabian Nights,” transferred to the region of facts. Faraday was not a mathematician. But if we turn to Kepler, who moved in the sphere of abstract calculation, we find precisely the same combination of characteristics. It was to Kepler, rather than to Copernicus, that we owe the establishment of the heliocentric theory of our universe, and Kepler, more than any man, was the precursor of Newton. It has been said that if Kepler had never lived it is difficult to conceive who could have taken his place and achieved his special part in the scientific creation of our universe. For that pioneering part was required a singular blend of seemingly opposed qualities. Only a wildly daring, original, and adventurous spirit could break away from the age-long traditions and rigid preconceptions which had ruled astronomy for thousands of years. Only an endlessly patient, careful, laborious, precise investigator could set up the new revolutionary conceptions needed to replace these traditions and preconceptions. Kepler supplied this rare combination of faculties. He possessed the most absurdly extravagant imagination; he developed a greater regard for accuracy in calculation than the world had ever known. He was willing to believe that the earth was a kind of animal, and would not have been surprised to find that it possessed lungs or gills. At the same time so set was he on securing the precise truth, so patiently laborious, that some of his most elaborate calculations were repeated, and without the help of logarithms, even seventy times. The two essential qualities that make the supreme artist in science have never been so clearly made manifest as in Kepler.