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[We have now to consider the work (other than botanical) which occupied the concluding six years of my father's life. A letter to his old friend Rev.

L. Blomefield (Jenyns), written in March, 1877, shows what was my father's estimate of his own powers of work at this time:--"My dear Jenyns (I see I have forgotten your proper names).--Your extremely kind letter has given me warm pleasure. As one gets old, one's thoughts turn back to the past rather than to the future, and I often think of the pleasant, and to me valuable, hours which I spent with you on the borders of the Fens.

"You ask about my future work; I doubt whether I shall be able to do much more that is new, and I always keep before my mind the example of poor old --, who in his old age had a cacoethes for writing. But I cannot endure doing nothing, so I suppose that I shall go on as long as I can without obviously making a fool of myself. I have a great mass of matter with respect to variation under nature; but so much has been published since the appearance of the 'Origin of Species,' that I very much doubt whether Iretain power of mind and strength to reduce the mass into a digested whole.

I have sometimes thought that I would try, but dread the attempt..."His prophecy proved to be a true one with regard to any continuation of any general work in the direction of Evolution, but his estimate of powers which could afterwards prove capable of grappling with the 'Power of Movement in Plants,' and with the work on 'Earthworms,' was certainly a low one.

The year 1876, with which the present chapter begins, brought with it a revival of geological work. He had been astonished, as I hear from Professor Judd, and as appears in his letters, to learn that his books on 'Volcanic Islands,' 1844, and on 'South America,' 1846, were still consulted by geologists, and it was a surprise to him that new editions should be required. Both these works were originally published by Messrs.

Smith and Elder, and the new edition of 1876 was also brought out by them.

This appeared in one volume with the title 'Geological Observations on the Volcanic Islands, and Parts of South America visited during the Voyage of H.M.S. "Beagle".' He has explained in the preface his reasons for leaving untouched the text of the original editions: "They relate to parts of the world which have been so rarely visited by men of science, that I am not aware that much could be corrected or added from observations subsequently made. Owing to the great progress which Geology has made within recent times, my views on some few points may be somewhat antiquated; but I have thought it best to leave them as they originally appeared."It may have been the revival of geological speculation, due to the revision of his early books, that led to his recording the observations of which some account is given in the following letter. Part of it has been published in Professor James Geikie's 'Prehistoric Europe,' chapters vii. and ix. (My father's suggestion is also noticed in Prof. Geikie's address on the 'Ice Age in Europe and North America,' given at Edinburgh, November 20, 1884.), a few verbal alterations having been made at my father's request in the passages quoted. Mr. Geikie lately wrote to me: "The views suggested in his letter as to the origin of the angular gravels, etc., in the South of England will, I believe, come to be accepted as the truth.

This question has a much wider bearing than might at first appear. In point of fact it solves one of the most difficult problems in Quaternary Geology--and has already attracted the attention of German geologists."]

CHARLES DARWIN TO JAMES GEIKIE.

Down, November 16, 1876.

My dear Sir, I hope that you will forgive me for troubling you with a very long letter.

But first allow me to tell you with what extreme pleasure and admiration Ihave just finished reading your 'Great Ice Age.' It seems to me admirably done, and most clear. Interesting as many chapters are in the history of the world, I do not think that any one comes [up] nearly to the glacial period or periods. Though I have steadily read much on the subject, your book makes the whole appear almost new to me.

I am now going to mention a small observation, made by me two or three years ago, near Southampton, but not followed out, as I have no strength for excursions. I need say nothing about the character of the drift there (which includes palaeolithic celts), for you have described its essential features in a few words at page 506. It covers the whole country [in an] even plain-like surface, almost irrespective of the present outline of the land.