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HISTORICAL VIEW OF THE

only legitimate ground of theory. The great problem ofthe system of the world we have found engaging the at-tention of two philosophers of pre-eminent celebrity: butone of these, though he laboured in the observatory toobtain accurate measures of the facts, failed in the com-prehensiveness of the theory he propounded : the othermade a happy adoption of a satisfactory theory, but itwas supported only by arguments from analogy andprobability, and the demonstrated insufficiency of theold hypotheses. We have now to turn our attention toa train of discoveries in which we shall find the truetheory supported on a firm basis of facts, and accord-ance with observation.

Kepler.

John Kepler was born at Weil, in the duchy ofWirtemberg , December the 21st, 1571- In infirmhealth from his birth, his life was more than once de-spaired of, yet he continued to make considerable pro-gress in his studies, both at the school of Maulbronn and at the college of Tubingen , under the tuition ofMoestlin. His time was here occupied, as he has him-self minutely related*, in the ardent pursuit of certainastronomical speculations, which evince at once the fer-tility of his imagination, and the indefatigable perse-verance with which he pursued and worked out the mostlaborious details of calculation required by these theo-ries, which, after all, turned out entirely unsubstantial,and which he discarded without hesitation on findingthem so.

Meanwhile he had acquired a reputation which atonce recommended him to be appointed professor ofastronomy at Gratz. Here, in the intervals of hispublic duties, he pursued these researches with unabatedardour. “ There were three things,” he says, “ in

* His own published correspondence supplies us with the most interest-ing details of his pursuits. Copious references to the original authoritieswill be found iu Drink water’s Life of Kepler.