(3/1. Extracts from Darwin's letters to Henslow were read before the Cambridge Philosophical Society on November 16th, 1835. Some of the letters were subsequently printed, in an 8vo pamphlet of 31 pages, dated December 1st, 1835, for private distribution among the members of the Society. A German translation by W. Preyer appeared in the "Deutsche Rundschau," June 1891.)
[15th August, 1832. Monte Video.]
We are now beating up the Rio Plata, and I take the opportunity of beginning a letter to you. I did not send off the specimens from Rio Janeiro, as I grudged the time it would take to pack them up. They are now ready to be sent off and most probably go by this packet. If so they go to Falmouth (where Fitz-Roy has made arrangements) and so will not trouble your brother's agent in London. When I left England I was not fully aware how essential a kindness you offered me when you undertook to receive my boxes. I do not know what I should do without such head-quarters. And now for an apologetical prose about my collection: I am afraid you will say it is very small, but I have not been idle, and you must recollect what a very small show hundreds of species make. The box contains a good many geological specimens; I am well aware that the greater number are too small. But I maintain that no person has a right to accuse me, till he has tried carrying rocks under a tropical sun. I have endeavoured to get specimens of every variety of rock, and have written notes upon all. If you think it worth your while to examine any of them I shall be very glad of some mineralogical information, especially on any numbers between 1 and 254 which include Santiago rocks. By my catalogue I shall know which you may refer to. As for my plants, "pudet pigetque mihi." All I can say is that when objects are present which I can observe and particularise about, I cannot summon resolution to collect when I know nothing.
It is positively distressing to walk in the glorious forest amidst such treasures and feel they are all thrown away upon one. My collection from the Abrolhos is interesting, as I suspect it nearly contains the whole flowering vegetation--and indeed from extreme sterility the same may almost be said of Santiago. I have sent home four bottles with animals in spirits, I have three more, but would not send them till I had a fourth. I shall be anxious to hear how they fare. I made an enormous collection of Arachnidae at Rio, also a good many small beetles in pill boxes, but it is not the best time of year for the latter. Amongst the lower animals nothing has so much interested me as finding two species of elegantly coloured true Planaria inhabiting the dewy forest! The false relation they bear to snails is the most extraordinary thing of the kind I have ever seen. In the same genus (or more truly family) some of the marine species possess an organisation so marvellous that I can scarcely credit my eyesight. Every one has heard of the discoloured streaks of water in the equatorial regions. One I examined was owing to the presence of such minute Oscillariae that in each square inch of surface there must have been at least one hundred thousand present. After this I had better be silent, for you will think me a Baron Munchausen amongst naturalists. Most assuredly I might collect a far greater number of specimens of Invertebrate animals if I took less time over each; but I have come to the conclusion that two animals with their original colour and shape noted down will be more valuable to naturalists than six with only dates and place. I hope you will send me your criticisms about my collection; and it will be my endeavour that nothing you say shall be lost on me. I would send home my writings with my specimens, only I find I have so repeatedly occasion to refer back that it would be a serious loss to me. I cannot conclude about my collection without adding that I implicitly trust in your keeping an exact account against all the expense of boxes, etc., etc. At this present minute we are at anchor in the mouth of the river, and such a strange scene as it is. Everything is in flames--the sky with lightning, the water with luminous particles, and even the very masts are pointed with a blue flame. I expect great interest in scouring over the plains of Monte Video, yet I look back with regret to the Tropics, that magic lure to all naturalists. The delight of sitting on a decaying trunk amidst the quiet gloom of the forest is unspeakable and never to be forgotten. How often have I then wished for you. When I see a banana I well recollect admiring them with you in Cambridge--little did I then think how soon I should eat their fruit.
August 15th. In a few days the box will go by the "Emulous" packet (Capt. Cooke) to Falmouth and will be forwarded to you. This letter goes the same way, so that if in course of due time you do not receive the box, will you be kind enough to write to Falmouth? We have been here (Monte Video) for some time; but owing to bad weather and continual fighting on shore, we have scarcely ever been able to walk in the country. I have collected during the last month nothing, but to-day I have been out and returned like Noah's Ark with animals of all sorts. I have to-day to my astonishment found two Planariae living under dry stones: ask L. Jenyns if he has ever heard of this fact. I also found a most curious snail, and spiders, beetles, snakes, scorpions ad libitum, and to conclude shot a Cavia weighing a cwt.--On Friday we sail for the Rio Negro, and then will commence our real wild work. I look forward with dread to the wet stormy regions of the south, but after so much pleasure I must put up with some sea-sickness and misery.
LETTER 4. TO J.S. HENSLOW. Monte Video, 24th November 1832.
We arrived here on the 24th of October, after our first cruise on the coast of Patagonia. North of the Rio Negro we fell in with some little schooners employed in sealing: to save the loss of time in surveying the intricate mass of banks, Capt. Fitz-Roy has hired two of them and has put officers on them. It took us nearly a month fitting them out; as soon as this was finished we came back here, and are now preparing for a long cruise to the south. I expect to find the wild mountainous country of Terra del Fuego very interesting, and after the coast of Patagonia I shall thoroughly enjoy it.—I had hoped for the credit of Dame Nature, no such country as this last existed; in sad reality we coasted along 240 miles of sand hillocks; I never knew before, what a horrid ugly object a sand hillock is. The famed country of the Rio Plata in my opinion is not much better: an enormous brackish river, bounded by an interminable green plain is enough to make any naturalist groan. So Hurrah for Cape Horn and the Land of Storms. Now that I have had my growl out, which is a privilege sailors take on all occasions, I will turn the tables and give an account of my doing in Nat. History. I must have one more growl: by ill luck the French Government has sent one of its collectors to the Rio Negro, where he has been working for the last six months, and is now gone round the Horn. So that I am very selfishly afraid he will get the cream of all the good things before me. As I have nobody to talk to about my luck and ill luck in collecting, I am determined to vent it all upon you. I have been very lucky with fossil bones; I have fragments of at least 6 distinct animals: as many of them are teeth, I trust, shattered and rolled as they have been, they will be recognised. I have paid all the attention I am capable of to their geological site; but of course it is too long a story for here. 1st, I have the tarsi and metatarsi very perfect of a Cavia; 2nd, the upper jaw and head of some very large animal with four square hollow molars and the head greatly protruded in front. I at first thought it belonged either to the Megalonyx or Megatherium (4/1. The animal may probably have been Grypotherium Darwini, Ow. The osseous plates mentioned below must have belonged to one of the Glyptodontidae, and not to Megatherium. We are indebted to Mr. Kerr for calling our attention to a passage in Buckland's "Bridgewater Treatise" (Volume II., page 20, note), where bony armour is ascribed to Megatherium.); in confirmation of this in the same formation I found a large surface of the osseous polygonal plates, which "late observations" (what are they?) show belong to the Megatherium. Immediately I saw this I thought they must belong to an enormous armadillo, living species of which genus are so abundant here. 3rd, The lower jaw of some large animal which, from the molar teeth, I should think belonged to the Edentata; 4th, some large molar teeth which in some respects would seem to belong to an enormous rodent; 5th, also some smaller teeth belonging to the same order. If it interests you sufficiently to unpack them, I shall be very curious to hear something about them. Care must be taken in this case not to confuse the tallies. They are mingled with marine shells which appear to me identical with what now exist. But since they were deposited in their beds several geological changes have taken place in the country. So much for the dead, and now for the living: there is a poor specimen of a bird which to my unornithological eyes appears to be a happy mixture of a lark, pigeon and snipe (No. 710). Mr. MacLeay himself never imagined such an inosculating creature: I suppose it will turn out to be some well-known bird, although it has quite baffled me. I have taken some interesting Amphibia; a new Trigonocephalus beautifully connecting in its habits Crotalus and the Viperidae, and plenty of new (as far as my knowledge goes) saurians. As for one little toad, I hope it may be new, that it may be christened "diabolicus." Milton must allude to this very individual when he talks of "squat like a toad"
(4/2. "...him [Satan] there they [Ithuriel and Zephon] found, Squat like a toad, close at the ear of Eve" ("Paradise Lost," Book IV., line 800).
"Formerly Milton's "Paradise Lost" had been my chief favourite, and in my excursions during the voyage of the 'Beagle,' when I could take only a single volume, I always chose Milton" ("Autobiography," page 69).); its colours are by Werner (4/3. Werner's "Nomenclature of Colours," Edinburgh, 1821.) ink black, vermilion red and buff orange. It has been a splendid cruise for me in Nat. History. Amongst the Pelagic Crustacea, some new and curious genera. In the Zoophytes some interesting animals. As for one Flustra, if I had not the specimen to back me up nobody would believe in its most anomalous structure. But as for novelty all this is nothing to a family of pelagic animals which at first sight appear like Medusae but are really highly organised. I have examined them repeatedly, and certainly from their structure it would be impossible to place them in any existing order. Perhaps Salpa is the nearest animal, although the transparency of the body is nearly the only character they have in common. I think the dried plants nearly contain all which were then (Bahia Blanca) flowering. All the specimens will be packed in casks. I think there will be three (before sending this letter I will specify dates, etc., etc.). I am afraid you will groan or rather the floor of the lecture room will when the casks arrive. Without you I should be utterly undone. The small cask contains fish: will you open it to see how the spirit has stood the evaporation of the Tropics. On board the ship everything goes on as well as possible; the only drawback is the fearful length of time between this and the day of our return. I do not see any limits to it. One year is nearly completed and the second will be so, before we even leave the east coast of S. America. And then our voyage may be said really to have commenced. I know not how I shall be able to endure it. The frequency with which I think of all the happy hours I have spent at Shrewsbury and Cambridge is rather ominous--I trust everything to time and fate and will feel my way as I go on.
November 24th. --We have been at Buenos Ayres for a week; it is a fine large city, but such a country, everything is mud, you can go nowhere, you can do nothing for mud. In the city I obtained much information about the banks of the Uruguay--I hear of limestone with shells, and beds of shells in every direction. I hope when we winter in the Plata to have a most interesting geological excursion into that country: I purchased fragments (Nos. 837-8) of some enormous bones, which I was assured belonged to the former giants!! I also procured some seeds--I do not know whether they are worth your accepting; if you think so I will get some more. They are in the box. I have sent to you by the "Duke of York" packet, commanded by Lieut. Snell, to Falmouth two large casks containing fossil bones, a small cask with fish and a box containing skins, spirit bottle, etc., and pillboxes with beetles. Would you be kind enough to open these latter as they are apt to become mouldy. With the exception of the bones the rest of my collection looks very scanty. Recollect how great a proportion of time is spent at sea. I am always anxious to hear in what state the things come and any criticisms about quantity or kind of specimens. In the smaller cask is part of a large head, the anterior portions of which are in the other large one. The packet has arrived and I am in a great bustle. You will not hear from me for some months.
LETTER 5. TO J.S. HENSLOW. Valparaiso, July 24th 1834.
A box has just arrived in which were two of your most kind and affectionate letters. You do not know how happy they have made me. One is dated December 15th, 1833, the other January 15th of the same year! By what fatality it did not arrive sooner I cannot conjecture; I regret it much, for it contains the information I most wanted, about manner of packing, etc., etc.: roots with specimens of plants, etc., etc. This I suppose was written after the reception of my first cargo of specimens. Not having heard from you until March of this year I really began to think that my collections were so poor, that you were puzzled what to say; the case is now quite on the opposite tack; for you are guilty of exciting all my vain feelings to a most comfortable pitch; if hard work will atone for these thoughts, I vow it shall not be spared. It is rather late, but I will allude to some remarks in the January letter; you advise me to send home duplicates of my notes; I have been aware of the advantage of doing so; but then at sea to this day, I am invariably sick, excepting on the finest days, at which times with pelagic animals around me, I could never bring myself to the task--on shore the most prudent person could hardly expect such a sacrifice of time. My notes are becoming bulky. I have about 600 small quarto pages full; about half of this is Geology--the other imperfect descriptions of animals; with the latter I make it a rule only to describe those parts or facts, which cannot be seen in specimens in spirits. I keep my private Journal distinct from the above. (N.B. this letter is a most untidy one, but my mind is untidy with joy; it is your fault, so you must take the consequences.) With respect to the land Planariae, unquestionably they are not molluscous animals. I read your letters last night, this morning I took a little walk; by a curious coincidence, I found a new white species of Planaria, and a new to me Vaginulus (third species which I have found in S. America) of Cuvier. Amongst the marine mollusques I have seen a good many genera, and at Rio found one quite new one. With respect to the December letter, I am very glad to hear the four casks arrived safe; since which time you have received another cargo, with the bird skins about which you did not understand me. Have any of the B. Ayrean seeds produced plants? From the Falklands I acknowledged a box and letter from you; with the letter were a few seeds from Patagonia. At present I have specimens enough to make a heavy cargo, but shall wait as much longer as possible, because opportunities are not now so good as before. I have just got scent of some fossil bones of a MAMMOTH; what they may be I do not know, but if gold or galloping will get them they shall be mine. You tell me you like hearing how I am going on and what doing, and you well may imagine how much I enjoy speaking to any one upon subjects which I am always thinking about, but never have any one to talk to [about]. After leaving the Falklands we proceeded to the Rio S. Cruz, following up the river till within twenty miles of the Cordilleras. Unfortunately want of provisions compelled us to return. This expedition was most important to me as it was a transverse section of the great Patagonian formation. I conjecture (an accurate examination of fossils may possibly determine the point) that the main bed is somewhere about the Miocene period (using Mr. Lyell's expression); I judge from what I have seen of the present shells of Patagonia. This bed contains an ENORMOUS field of lava. This is of some interest, as being a rude approximation to the age of the volcanic part of the great range of the Andes. Long before this it existed as a slate and porphyritic line of hills. I have collected a tolerable quantity of information respecting the period and forms of elevations of these plains. I think these will be interesting to Mr. Lyell; I had deferred reading his third volume till my return: you may guess how much pleasure it gave me; some of his woodcuts came so exactly into play that I have only to refer to them instead of redrawing similar ones. I had my barometer with me, I only wish I had used it more in these plains. The valley of S. Cruz appears to me a very curious one; at first it quite baffled me. I believe I can show good reasons for supposing it to have been once a northern straits like to that of Magellan. When I return to England you will have some hard work in winnowing my Geology; what little I know I have learnt in such a curious fashion that I often feel very doubtful about the number of grains [of value?]. Whatever number they may turn out, I have enjoyed extreme pleasure in collecting them. In T. del Fuego I collected and examined some corallines; I have observed one fact which quite startled me: it is that in the genus Sertularia (taken in its most restricted form as [used] by Lamoureux) and in two species which, excluding comparative expressions, I should find much difficulty in describing as different, the polypi quite and essentially differed in all their most important and evident parts of structure. I have already seen enough to be convinced that the present families of corallines as arranged by Lamarck, Cuvier, etc., are highly artificial. It appears that they are in the same state [in] which shells were when Linnaeus left them for Cuvier to rearrange. I do so wish I was a better hand at dissecting, I find I can do very little in the minute parts of structure; I am forced to take a very rough examination as a type for different classes of structure. It is most extraordinary I can nowhere see in my books one single description of the polypus of any one coralline excepting Alcyonium Lobularia of Savigny. I found a curious little stony Cellaria (5/1. Cellaria, a genus of Bryozoa, placed in the section Flustrina of the Suborder Chilostomata.) (a new genus) each cell provided with long toothed bristle, these are capable of various and rapid motions. This motion is often simultaneous, and can be produced by irritation. This fact, as far as I can see, is quite isolated in the history of zoophytes (excepting the Flustra with an organ like a vulture's head); it points out a much more intimate relation between the polypi than Lamarck is willing to allow. I forgot whether I mentioned having seen something of the manner of propagation in that most ambiguous family, the corallines; I feel pretty well convinced if they are not plants they are not zoophytes. The "gemmule" of a Halimeda contained several articulations united, ready to burst their envelope, and become attached to some basis. I believe in zoophytes universally the gemmule produces a single polypus, which afterwards or at the same time grows with its cell or single articulation.
The "Beagle" left the Sts. of Magellan in the middle of winter; she found her road out by a wild unfrequented channel; well might Sir J. Narborough call the west coast South Desolation, "because it is so desolate a land to behold." We were driven into Chiloe by some very bad weather. An Englishman gave me three specimens of that very fine Lucanoidal insect which is described in the "Camb. Phil. Trans." (5/2. "Description of Chiasognathus Grantii, a new Lucanideous Insect, etc." by J.F. Stephens ("Trans. Camb. Phil. Soc." Volume IV., page 209, 1833.), two males and one female. I find Chiloe is composed of lava and recent deposits. The lavas are curious from abounding in, or rather being in parts composed of pitchstone. If we go to Chiloe in the summer, I shall reap an entomological harvest. I suppose the Botany both there and in Chili is well-known.
I forgot to state that in the four cargoes of specimens there have been sent three square boxes, each containing four glass bottles. I mention this in case they should be stowed beneath geological specimens and thus escape your notice, perhaps some spirit may be wanted in them. If a box arrives from B. Ayres with a Megatherium head the other unnumbered specimens, be kind enough to tell me, as I have strong fears for its safety. We arrived here the day before yesterday; the views of the distant mountains are most sublime and the climate delightful; after our long cruise in the damp gloomy climates of the south, to breathe a clear dry air and feel honest warm sunshine, and eat good fresh roast beef must be the summum bonum of human life. I do not like the look of the rocks half so much as the beef, there is too much of those rather insipid ingredients, mica, quartz and feldspar. Our plans are at present undecided; there is a good deal of work to the south of Valparaiso and to the north an indefinite quantity. I look forward to every part with interest. I have sent you in this letter a sad dose of egotism, but recollect I look up to you as my father in Natural History, and a son may talk about himself to his father. In your paternal capacity as proproctor what a great deal of trouble you appear to have had. How turbulent Cambridge is become. Before this time it will have regained its tranquillity. I have a most schoolboy-like wish to be there, enjoying my holidays. It is a most comfortable reflection to me, that a ship being made of wood and iron, cannot last for ever, and therefore this voyage must have an end.
October 28th. This letter has been lying in my portfolio ever since July; I did not send it away because I did not think it worth the postage; it shall now go with a box of specimens. Shortly after arriving here I set out on a geological excursion, and had a very pleasant ramble about the base of the Andes. The whole country appears composed of breccias (and I imagine slates) which universally have been modified and oftentimes completely altered by the action of fire. The varieties of porphyry thus produced are endless, but nowhere have I yet met with rocks which have flowed in a stream; dykes of greenstone are very numerous. Modern volcanic action is entirely shut up in the very central parts (which cannot now be reached on account of the snow) of the Cordilleras. In the south of the R. Maypu I examined the Tertiary plains, already partially described by M. Gay. (5/3. "Rapport fait a l'Academie Royale des Sciences, sur les Travaux Geologiques de M. Gay," by Alex. Brongniart ("Ann. Sci. Nat." Volume XXVIII., page 394, 1833.) The fossil shells appear to me to be far more different from the recent ones than in the great Patagonian formation;
it will be curious if an Eocene and Miocene (recent there is abundance of) could be proved to exist in S. America as well as in Europe. I have been much interested by finding abundance of recent shells at an elevation of 1,300 feet; the country in many places is scattered over with shells but these are all littoral ones. So that I suppose the 1,300 feet elevation must be owing to a succession of small elevations such as in 1822. With these certain proofs of the recent residence of the ocean over all the lower parts of Chili, the outline of every view and the form of each valley possesses a high interest. Has the action of running water or the sea formed this deep ravine? was a question which often arose in my mind and generally was answered by finding a bed of recent shells at the bottom. I have not sufficient arguments, but I do not believe that more than a small fraction of the height of the Andes has been formed within the Tertiary period. The conclusion of my excursion was very unfortunate, I became unwell and could hardly reach this place. I have been in bed for the last month, but am now rapidly getting well. I had hoped during this time to have made a good collection of insects but it has been impossible: I regret the less because Chiloe fairly swarms with collectors; there are more naturalists in the country, than carpenters or shoemakers or any other honest trade.
In my letter from the Falkland Islands I said I had fears about a box with a Megatherium. I have since heard from B. Ayres that it went to Liverpool by the brig "Basingwaithe." If you have not received it, it is I think worth taking some trouble about. In October two casks and a jar were sent by H.M.S. "Samarang" via Portsmouth. I have no doubt you have received them. With this letter I send a good many bird skins; in the same box with them, there is a paper parcel containing pill boxes with insects. The other pill boxes require no particular care. You will see in two of these boxes some dried Planariae (terrestrial), the only method I have found of preserving them (they are exceedingly brittle). By examining the white species I understand some little of the internal structure. There are two small parcels of seeds. There are some plants which I hope may interest you, or at least those from Patagonia where I collected every one in flower. There is a bottle clumsily but I think securely corked containing water and gas from the hot baths of Cauquenes seated at foot of Andes and long celebrated for medicinal properties. I took pains in filling and securing both water and gas. If you can find any one who likes to analyze them, I should think it would be worth the trouble. I have not time at present to copy my few observations about the locality, etc., etc., [of] these springs. Will you tell me how the Arachnidae which I have sent home, for instance those from Rio, appear to be preserved. I have doubts whether it is worth while collecting them.
We sail the day after to-morrow: our plans are at last limited and definite; I am delighted to say we have bid an eternal adieu to T. del
Fuego. The "Beagle" will not proceed further south than C. Tres Montes; from which point we survey to the north. The Chonos Archipelago is delightfully unknown: fine deep inlets running into the Cordilleras--where we can steer by the light of a volcano. I do not know which part of the voyage now offers the most attractions. This is a shamefully untidy letter, but you must forgive me.
LETTER 6. TO J.S. HENSLOW. April 18th, 1835. Valparaiso.
I have just returned from Mendoza, having crossed the Cordilleras by two passes. This trip has added much to my knowledge of the geology of the country. Some of the facts, of the truth of which I in my own mind feel fully convinced, will appear to you quite absurd and incredible. I will give a very short sketch of the structure of these huge mountains. In the Portillo pass (the more southern one) travellers have described the Cordilleras to consist of a double chain of nearly equal altitude separated by a considerable interval. This is the case; and the same structure extends to the northward to Uspallata; the little elevation of the eastern line (here not more than 6,000-7,000 feet.) has caused it almost to be overlooked. To begin with the western and principal chain, we have, where the sections are best seen, an enormous mass of a porphyritic conglomerate resting on granite. This latter rock seems to form the nucleus of the whole mass, and is seen in the deep lateral valleys, injected amongst, upheaving, overturning in the most extraordinary manner, the overlying strata. The stratification in all the mountains is beautifully distinct and from a variety in the colour can be seen at great distances. I cannot imagine any part of the world presenting a more extraordinary scene of the breaking up of the crust of the globe than the very central parts of the Andes. The upheaval has taken place by a great number of (nearly) N. and S. lines; which in most cases have formed as many anticlinal and synclinal ravines; the strata in the highest pinnacles are almost universally inclined at an angle from 70 deg to 80 deg. I cannot tell you how I enjoyed some of these views--it is worth coming from England, once to feel such intense delight; at an elevation from 10 to 12,000 feet there is a transparency in the air, and a confusion of distances and a sort of stillness which gives the sensation of being in another world, and when to this is joined the picture so plainly drawn of the great epochs of violence, it causes in the mind a most strange assemblage of ideas.
The formation I call Porphyritic Conglomerates is the most important and most developed one in Chili: from a great number of sections I find it a true coarse conglomerate or breccia, which by every step in a slow gradation passes into a fine claystone-porphyry; the pebbles and cement becoming porphyritic till at last all is blended in one compact rock. The porphyries are excessively abundant in this chain. I feel sure at least 4/5ths of them have been thus produced from sedimentary beds in situ. There are porphyries which have been injected from below amongst strata, and others ejected, which have flowed in streams; it is remarkable, and I could show specimens of this rock produced in these three methods, which cannot be distinguished. It is a great mistake considering the Cordilleras here as composed of rocks which have flowed in streams. In this range I nowhere saw a fragment, which I believe to have thus originated, although the road passes at no great distance from the active volcanoes. The porphyries, conglomerate, sandstone and quartzose sandstone and limestones alternate and pass into each other many times, overlying (where not broken through by the granite) clay-slate. In the upper parts, the sandstone begins to alternate with gypsum, till at last we have this substance of a stupendous thickness. I really think the formation is in some places (it varies much) nearly 2,000 feet thick, it occurs often with a green (epidote?) siliceous sandstone and snow-white marble; it resembles that found in the Alps in containing large concretions of a crystalline marble of a blackish grey colour. The upper beds which form some of the higher pinnacles consist of layers of snow-white gypsum and red compact sandstone, from the thickness of paper to a few feet, alternating in an endless round. The rock has a most curiously painted appearance. At the pass of the Peuquenes in this formation, where however a black rock like clay-slate, without many laminae, occurring with a pale limestone, has replaced the red sandstone, I found abundant impressions of shells. The elevation must be between 12 and 13,000 feet. A shell which I believe is the Gryphaea is the most abundant--an Ostrea, Turratella, Ammonites, small bivalves, Terebratulae (?). Perhaps some good conchologist (6/1. Some of these genera are mentioned by Darwin ("Geol. Obs." page 181) as having been named for him by M. D'Orbigny.) will be able to give a guess, to what grand division of the formations of Europe these organic remains bear most resemblance. They are exceedingly imperfect and few. It was late in the season and the situation particularly dangerous for snow-storms. I did not dare to delay, otherwise a grand harvest might have been reaped. So much for the western line; in the Portillo pass, proceeding eastward, we meet an immense mass of conglomerate, dipping to the west 45 deg, which rest on micaceous sandstone, etc., etc., upheaved and converted into quartz-rock penetrated by dykes from the very grand mass of protogine (large crystals of quartz, red feldspar, and occasional little chlorite). Now this conglomerate which reposes on and dips from the protogene 45 deg consists of the peculiar rocks of the first described chain, pebbles of the black rock with shells, green sandstone, etc., etc. It is hence manifest that the upheaval (and deposition at least of part) of the grand eastern chain is entirely posterior to the western. To the north in the Uspallata pass, we have also a fact of the same class. Bear this in mind: it will help to make you believe what follows. I have said the Uspallata range is geologically, although only 6,000-7,000 feet, a continuation of the grand eastern chain. It has its nucleus of granite, consists of grand beds of various crystalline rocks, which I can feel no doubt are subaqueous lavas alternating with sandstone, conglomerates and white aluminous beds (like decomposed feldspar) with many other curious varieties of sedimentary deposits. These lavas and sandstones alterate very many times, and are quite conformable one to the other. During two days of careful examination I said to myself at least fifty times, how exactly like (only rather harder) these beds are to those of the upper Tertiary strata of Patagonia, Chiloe and Concepcion, without the possible identity ever having occurred to me. At last there was no resisting the conclusion. I could not expect shells, for they never occur in this formation; but lignite or carbonaceous shale ought to be found. I had previously been exceedingly puzzled by meeting in the sandstone, thin layers (few inches to feet thick) of a brecciated pitchstone. I strongly suspect the underlying granite has altered such beds into this pitchstone. The silicified wood (particularly characteristic) was yet absent. The conviction that I was on the Tertiary strata was so strong by this time in my mind, that on the third day in the midst of lavas and [? masses] of granite I began my apparently forlorn hunt. How do you think I succeeded? In an escarpement of compact greenish sandstone, I found a small wood of petrified trees in a vertical position, or rather the strata were inclined about 20-30 deg to one point and the trees 70 deg to the opposite one. That is, they were before the tilt truly vertical. The sandstone consists of many layers, and is marked by the concentric lines of the bark (I have specimens); 11 are perfectly silicified and resemble the dicotyledonous wood which I have found at Chiloe and Concepcion (6/2. "Geol. Obs." page 202. Specimens of the silicified wood were examined by Robert Brown, and determined by him as coniferous, "partaking of the characters of the Araucarian tribe, with some curious points of affinity with the yew."); the others (30-40) I only know to be trees from the analogy of form and position; they consist of snow-white columns (like Lot's wife) of coarsely crystalline carb. of lime. The largest shaft is 7 feet. They are all close together, within 100 yards, and about the same level: nowhere else could I find any. It cannot be doubted that the layers of fine sandstone have quietly been deposited between a clump of trees which were fixed by their roots. The sandstone rests on lava, is covered by a great bed apparently about 1,000 feet thick of black augitic lava, and over this there are at least 5 grand alternations of such rocks and aqueous sedimentary deposits, amounting in thickness to several thousand feet. I am quite afraid of the only conclusion which I can draw from this fact, namely that there must have been a depression in the surface of the land to that amount. But neglecting this consideration, it was a most satisfactory support of my presumption of the Tertiary (I mean by Tertiary, that the shells of the period were closely allied, or some identical, to those which now live, as in the lower beds of Patagonia) age of this eastern chain. A great part of the proof must remain upon my ipse dixit of a mineralogical resemblance with those beds whose age is known, and the character of which resemblance is to be subject to infinite variation, passing from one variety to another by a concretionary structure. I hardly expect you to believe me, when it is a consequence of this view that granite, which forms peaks of a height probably of 14,000 feet, has been fluid in the Tertiary period; that strata of that period are altered by its heat, and are traversed by dykes from the mass. That these strata have also probably undergone an immense depression, that they are now inclined at high angles and form regular or complicated anticlinal lines. To complete the climax and seal your disbelief, these same sedimentary strata and lavas are traversed by VERY NUMEROUS, true metallic veins of iron, copper, arsenic, silver and gold, and these can be traced to the underlying granite. A gold mine has been worked close to the clump of silicified trees. If when you see my specimens, sections and account, you should think that there is pretty strong presumptive evidence of the above facts, it appears very important; for the structure, and size of this chain will bear comparison with any in the world, and that this all should have been produced in so very recent a period is indeed wonderful. In my own mind I am quite convinced of the reality of this. I can anyhow most conscientiously say that no previously formed conjecture warped my judgment. As I have described so did I actually observe the facts. But I will have some mercy and end this most lengthy account of my geological trip.
On some of the large patches of perpetual snow, I found the famous red snow of the Arctic countries; I send with this letter my observations and a piece of paper on which I tried to dry some specimens. If the fact is new and you think it worth while, either yourself examine them or send them to whoever has described the specimens from the north and publish a notice in any of the periodicals. I also send a small bottle with two lizards, one of them is viviparous as you will see by the accompanying notice. A M. Gay--a French naturalist--has already published in one of the newspapers of this country a similar statement and probably has forwarded to Paris some account; as the fact appears singular would it not be worth while to hand over the specimens to some good lizardologist and comparative anatomist to publish an account of their internal structure? Do what you think fit.
This letter will go with a cargo of specimens from Coquimbo. I shall write to let you know when they are sent off. In the box there are two bags of seeds, one [from the] valleys of the Cordilleras 5,000-10,000 feet high, the soil and climate exceedingly dry, soil very light and stony, extremes in temperature; the other chiefly from the dry sandy Traversia of Mendoza 3,000 feet more or less. If some of the bushes should grow but not be healthy, try a slight sprinkling of salt and saltpetre. The plain is saliferous. All the flowers in the Cordilleras appear to be autumnal flowerers--they were all in blow and seed, many of them very pretty. I gathered them as I rode along on the hill sides. If they will but choose to come up, I have no doubt many would be great rarities. In the Mendoza bag there are the seeds or berries of what appears to be a small potato plant with a whitish flower. They grow many leagues from where any habitation could ever have existed owing to absence of water. Amongst the Chonos dried plants, you will see a fine specimen of the wild potato, growing under a most opposite climate, and unquestionably a true wild potato. It must be a distinct species from that of the Lower Cordilleras one. Perhaps as with the banana, distinct species are now not to be distinguished in their varieties produced by cultivation. I cannot copy out the few remarks about the Chonos potato. With the specimens there is a bundle of old papers and notebooks. Will you take care of them; in case I should lose my notes, these might be useful. I do not send home any insects because they must be troublesome to you, and now so little more of the voyage remains unfinished I can well take charge of them. In two or three days I set out for Coquimbo by land; the "Beagle" calls for me in the beginning of June. So that I have six weeks more to enjoy geologising over these curious mountains of Chili. There is at present a bloody revolution in Peru. The Commodore has gone there, and in the hurry has carried our letters with him; perhaps amongst them there will be one from you. I wish I had the old Commodore here, I would shake some consideration for others into his old body. From Coquimbo you will again hear from me.
This is the last letter which I shall ever write to you from the shores of America, and for this reason I send it. In a few days time the "Beagle" will sail for the Galapagos Islands. I look forward with joy and interest to this, both as being somewhat nearer to England and for the sake of having a good look at an active volcano. Although we have seen lava in abundance, I have never yet beheld the crater. I sent by H.M.S. "Conway" two large boxes of specimens. The "Conway" sailed the latter end of June. With them were letters for you, since that time I have travelled by land from Valparaiso to Copiapo and seen something more of the Cordilleras. Some of my geological views have been, subsequently to the last letter, altered. I believe the upper mass of strata is not so very modern as I supposed. This last journey has explained to me much of the ancient history of the Cordilleras. I feel sure they formerly consisted of a chain of volcanoes from which enormous streams of lava were poured forth at the bottom of the sea. These alternate with sedimentary beds to a vast thickness; at a subsequent period these volcanoes must have formed islands, from which have been produced strata of several thousand feet thick of coarse conglomerate. (7/1. See "Geological Observations on South America" (London, 1846), Chapter VII.: "Central Chile; Structure of the
Cordillera.") These islands were covered with fine trees; in the conglomerate, I found one 15 feet in circumference perfectly silicified to the very centre. The alternations of compact crystalline rocks (I cannot doubt subaqueous lavas), and sedimentary beds, now upheaved fractured and indurated, form the main range of the Andes. The formation was produced at the time when ammonites, gryphites, oysters, Pecten, Mytilus, etc., etc., lived. In the central parts of Chili the structure of the lower beds is rendered very obscure by the metamorphic action which has rendered even the coarsest conglomerates porphyritic. The Cordilleras of the Andes so worthy of admiration from the grandeur of their dimensions, rise in dignity when it is considered that since the period of ammonites, they have formed a marked feature in the geography of the globe. The geology of these mountains pleased me in one respect; when reading Lyell, it had always struck me that if the crust of the world goes on changing in a circle, there ought to be somewhere found formations which, having the age of the great European Secondary beds, should possess the structure of Tertiary rocks or those formed amidst islands and in limited basins. Now the alternations of lava and coarse sediment which form the upper parts of the Andes, correspond exactly to what would accumulate under such circumstances. In consequence of this, I can only very roughly separate into three divisions the varying strata (perhaps 8,000 feet thick) which compose these mountains. I am afraid you will tell me to learn my ABC to know quartz from feldspar before I indulge in such speculations. I lately got hold of a report on M. Dessalines D'Orbigny's labours in S. America (7/2. "Voyage dans l'Amerique Meridionale, etc." (A. Dessalines D'Orbigny).); I experienced rather a debasing degree of vexation to find he has described the Geology of the Pampas, and that I have had some hard riding for nothing, it was however gratifying that my conclusions are the same, as far as I can collect, with his results. It is also capital that the whole of Bolivia will be described. I hope to be able to connect his geology of that country with mine of Chili. After leaving Copiapo, we touched at Iquique. I visited but do not quite understand the position of the nitrate of soda beds. Here in Peru, from the state of anarchy, I can make no expedition.
I hear from home, that my brother is going to send me a box with books, and a letter from you. It is very unfortunate that I cannot receive this before we reach Sydney, even if it ever gets safely so far. I shall not have another opportunity for many months of again writing to you. Will you have the charity to send me one more letter (as soon as this reaches you) directed to the C. of Good Hope. Your letters besides affording me the greatest delight always give me a fresh stimulus for exertion. Excuse this geological prosy letter, and farewell till you hear from me at Sydney, and see me in the autumn of 1836.
LETTER 8. TO JOSIAH WEDGWOOD. [Shrewsbury, October 5th, 1836.]
The "Beagle" arrived at Falmouth on Sunday evening, and I reached home late last night. My head is quite confused with so much delight, but I cannot allow my sisters to tell you first how happy I am to see all my dear friends again. I am obliged to return in three or four days to London, where the "Beagle" will be paid off, and then I shall pay Shrewsbury a longer visit. I am most anxious once again to see Maer, and all its inhabitants, so that in the course of two or three weeks, I hope in person to thank you, as being my first Lord of the Admiralty. (8/1. Readers of the "Life and Letters" will remember that it was to Josiah Wedgwood that Darwin owed the great opportunity of his life ("Life and Letters," Volume I., page 59), and it was fitting that he should report himself to his "first Lord of the Admiralty." The present letter clears up a small obscurity to which Mr. Poulton has called attention ("Charles Darwin and the Theory of Natural Selection," "Century" Series, 1896, page 25). Writing to Fitz-Roy from Shrewsbury on October 6th, Darwin says, "I arrived here yesterday morning at breakfast time." This refers to his arrival at his father's house, after having slept at the inn. The date of his arrival in Shrewsbury was, therefore, October 4th, as given in the "Life and Letters," I., page 272.) The entries in his Diary are:--October 2, 1831. Took leave of my home.
October 4, 1836. Reached Shrewsbury after absence of 5 years and 2 days.) I am so very happy I hardly know what I am writing. Believe me your most affectionate nephew,
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