The help derived from these departed colleagues, Henry Sidgwick and Edmund Gurney, although of a kind and quantity absolutely essential to the existence of this work, is not easy to define in all its fulness under the changed circumstances of to-day. There was indeed much which is measurable;-much of revision of previous work of my own, of collaborative experiments, of original thought and discovery. Large quotations purposely introduced from Edmund Gurney indicate, although imperfectly, how closely interwoven our work on all these subjects continued to be until his death. But the benefit which I drew from the association went deeper still. The conditions under which this inquiry was undertaken were such as to emphasise the need of some intimate moral support. A recluse, perhaps, or an eccentric, -or a man living mainly with his intellectual inferiors, may find it easy to work steadily and confidently at a task which he knows that the bulk of educate