Till arriving at Teneriffe (we did not touch at Madeira) I was scarcely out of my hammock, and really suffered more than you can well imagine from such a cause. At Santa Cruz, whilst looking amongst the clouds for the Peak, and repeating to myself Humboldt's sublime descriptions, it was announced we must perform twelve days' strict quarantine. We had made a short passage, so "Up jib," and away for St. Jago. You will say all this sounds very bad, and so it was; but from that to the present time it has been nearly one scene of continual enjoyment. A net over the stern kept me at full work till we arrived at St. Jago. Here we spent three most delightful weeks. The geology was pre-eminently interesting, and I believe quite new; there are some facts on a large scale of upraised coast (which is an excellent epoch for all the volcanic rocks to date from), that would interest Mr. Lyell. One great source of perplexity to me is an utter ignorance whether I note the right facts, and whether they are of sufficient importance to interest others. In the one thing collecting I cannot go wrong. St. Jago is singularly barren, and produces few plants or insects, so that my hammer was my usual companion, and in its company most delightful hours I spent. On the coast I collected many marine animals, chiefly gasteropodous (I think some new). I examined pretty accurately a Caryopyllia, and, if my eyes are not bewitched, former descriptions have not the slightest resemblance to the animal. I took several specimens of an Octopus which possessed a most marvellous power of changing its colours, equalling any chameleon, and evidently accommodating the changes to the colour of the ground which it passed over. Yellowish green, dark brown, and red, were the prevailing colours; this fact appears to be new, as far as I can find out. Geology and the invertebrate animals will be my chief object of pursuit through the whole voyage. We then sailed for Bahia, and touched at the rock of St. Paul. This is a serpentine formation. Is it not the only island in the Atlantic which is not volcanic? We likewise stayed a few hours at Fernando Noronha; a tremendous surf was running so that a boat was swamped, and the Captain would not wait. I find my life on board when we are on blue water most delightful, so very comfortable and quiet--it is almost impossible to be idle, and that for me is saying a good deal. Nobody could possibly be better fitted in every respect for collecting than I am; many cooks have not spoiled the broth this time. Mr. Brown's little hints about microscopes, etc., have been invaluable. I am well off in books, the 'Dictionnaire Classique' IS MOST USEFUL. If you should think of any thing or book that would be useful to me, if you would write one line, E. Darwin, Wyndham Club, St. James's Street, he will procure them, and send them with some other things to Monte Video, which for the next year will be my headquarters.