Mr Francis Darwin has told us that the nature and extent of his father's sufferings--so patiently and uncomplainingly borne--were never fully known, even to his own children, but only to the faithful wife who devoted her whole life to the care of his health. As is well known, Darwin seldom visited at other houses, besides those of immediate relatives, or the hydropathic establishment at which he sought relief from his illness. But he was in the habit of sometimes, when in London, calling upon David Forbes the mineralogist (a younger brother of Edward Forbes) then living in York Street, Portman Square. The bonds of union between Charles Darwin and David Forbes were, first, that they had both travelled extensively in South America, and secondly, that both were greatly interested in methods of preserving and making available for future reference all notes and memoranda collected from various sources. David Forbes devoted to the purpose a large room with the most elaborate system of pigeon-holes, about which he told me that Darwin was greatly excited. He also mentioned to me that, on one or more occasions, while Darwin was in his house, pains of such a violent character had seized him that he had been compelled to lie down for a time and had occasioned his host the greatest alarm. It must always therefore be remembered, in reading Darwin's works, what were the sad conditions under which they were produced. It seems to be doubtful to what extent his ill-health may be regarded as the result of an almost fatal malady, from which he suffered in South America, or as the effect of the constant and prolonged sea-sickness of which he was the victim during the five years' voyage. But certain it is that his work was carried on under no ordinary difficulties, and that it was only by the exercise of the sternest resolution, in devoting every moment of time that he was free from pain to his tasks, that he was able to accomplish his great undertakings. I do not think, however, that any unprejudiced reader will regard Darwin's literary work as standing in need of anything like an apology. He always aims--and I think succeeds--at conveying his meaning in simple and direct language; and in all his works there is manifest that undercurrent of quiet enthusiasm, which was so strikingly displayed in his conversation. It was delightful to witness the keen enjoyment with which he heard of any new fact or observation bearing on the pursuits in which he was engaged, and his generous nature always led him to attach an exaggerated value to any discovery or suggestion which might be brought to his knowledge--and to appraise the work of others above his own.