[As for the ordinary course of a day’s work, the more fitful energy and useless mornings of the earliest period in London were soon left behind.  He was never one of those portentously early risers who do a fair day’s work before other people are up; there was only one period, about 1873, when he had to be specially careful of his health, and, under Sir Andrew Clark’s regime, took riding exercise for an hour each day before starting for South Kensington, that he records the fact of doing any work before breakfast, and that was letter-writing.

Much of the day during the session, and still more when his lectures were over, would thus be spent in original research, or in the examination and description of fossils in his official duty as Paleontologist to the Survey.  As often as not, there would be a sitting of some Royal Commission to attend; committees of some learned society; meetings or dinners in the evening; if not, there would be an article to write or proofs to correct.  Indeed, the greater part of the work by which the world knows him best was done after dinner, and after a long day’s work in the lecture-room and laboratory.

He possessed a wonderful faculty for tearing out the heart of a book, reading it through at a gallop, but knowing what it said on all the points that interested him.  Of verbal memory he had very little; in spite of all his reading I do not believe he knew half a dozen consecutive lines of poetry by heart.  What he did know was the substance of what an author had written; how it fitted into his own scheme of knowledge; and where to find any point again when he wished to cite it.

In his biological studies his immense knowledge was firmly fixed in his mind by practical investigation; as is said above, he would take at second hand nothing for which he vouched in his teaching, and was always ready to repeat for himself the experiments of others, which determined questions of interest to him.  The citations, analyses, maps, with which he frequently accompanied his reading, were all part of the same method of acquiring facts and setting them in order within his mind.  So careful, indeed, was he in giving nothing at second hand, that one of his scientific friends reproached him with wasting his time upon unnecessary scientific work, to which competent investigators had already given the stamp of their authority.  “Poor—­,” was his comment afterwards, “if that is his own practice, his work will never live.”  On the literary side, he was omnivorous—­consuming everything, as Mr. Spencer put it, from fairy tales to the last volume on metaphysics.