In this same year (1837) the _History of the Inductive Sciences_ was published, to be followed in less than three years by the _Philosophy_ of the same. This encyclopædic publication—for the two books must be considered together—marks the conclusion of that part of his life which had been devoted, in the main, to pure science; and it gives the reason for his having thrown himself into occupations so diverse. It was not his habit to write on that which he had not completely mastered; and he therefore thought, wrote, and published on most of the separate sciences while tracing their history and developing their philosophy. In this rapid sketch we have not been able to do more than indicate the principal works which Whewell had had in hand. It must not be forgotten that at the same time he was engaged in a large and ever-increasing correspondence; writing letters—which, as he used to say himself, ought to be ‘postworthy’—not merely to scientific men, as we know from Mr Todhunter’s book, but—as we now know from Mrs Stair Douglas—to his sisters and other ladies, on all sorts of subjects which he thought would interest them. Then he was a wide reader, as is proved by notes he made on the books which he had read from 1817 to 1830: ‘books in almost all the languages of Europe; histories of all countries, ancient or modern; treatises on all sciences, moral and physical. Among the notes is an epitome of Kant’s _Kritik der reinen Vernunft_, a work which exercised a marked influence on all his speculations in mental philosophy.’ Whatever he read, he read thoroughly. Mr Todhunter illustrates this by a story given on the authority of one of his oldest friends. He was found reading Henry Taylor’s _Philip van Artevelde_, which then had just appeared. Not content with the poem alone, however, he had Froissart by his side, and was carefully comparing the modern drama with the ancient chronicle. Lastly—and we put the subject we are now about to mention last, not because it was least, but because it was, or ought to have been, the most important of all his occupations—he held the office of tutor of one of the three _sides_, as they were called, into which Trinity College was then divided, first alone, and next in conjunction with Mr Perry, from 1823 to 1838.