More Letters of Charles Darwin Volume II

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My paper will be published immediately in the "Geological Transactions,"
and I will do myself the pleasure of sending you a copy in the course of
(as I hope) a week or ten days. A large part of it is theoretical, and
will be of little interest to you; but the account of the Concepcion shock
of 1835 will, I think, be worth your perusal. I have understood from Mr.
Lyell that you believe in some connection between the state of the weather
and earthquakes. Under the very peculiar climate of Northern Chile, the
belief of the inhabitants in such connection can hardly, in my opinion, be
founded in error. It must possibly be worth your while to turn to pages
430-433 in my "Journal of Researches during the Voyage of the 'Beagle',"
where I have stated this circumstance. (479/3. "Journal of Researches
into the Natural History and Geology of the Countries visited during the
Voyage of H.M.S. 'Beagle' round the World." London, 1870, page 351.) On
the hypothesis of the crust of the earth resting on fluid matter, would the
influence of the moon (as indexed by the tides) affect the periods of the
shocks, when the force which causes them is just balanced by the resistance
of the solid crust? The fact you mention of the coincidence between the
earthquakes of Calabria and Scotland appears most curious. Your paper will
possess a high degree of interest to all geologists. I fancied that such
uniformity of action, as seems here indicated, was probably confined to
large continents, such as the Americas. How interesting a record of
volcanic phenomena in Iceland would be, now that you are collecting
accounts of every slight trembling in Scotland. I am astonished at their
frequency in that quiet country, as any one would have called it. I wish
it had been in my power to have contributed in any way to your researches
on this most interesting subject.

LETTER 480. TO L. HORNER.
Down, August 29th [1844].

I am greatly obliged for your kind note, and much pleased with its
contents. If one-third of what you say be really true, and not the verdict
of a partial judge (as from pleasant experience I much suspect), then
should I be thoroughly well contented with my small volume which, small as
it is, cost me much time. (480/1. "Geological Observations on the
Volcanic Islands visited during the Voyage of H.M.S. 'Beagle'": London,
1844. A French translation has been made by Professor Renard of Ghent, and
published by Reinwald of Paris in 1902.) The pleasure of observation amply
repays itself: not so that of composition; and it requires the hope of
some small degree of utility in the end to make up for the drudgery of
altering bad English into sometimes a little better and sometimes worse.
With respect to craters of elevation (480/2. "Geological Observations,"
pages 93-6.), I had no sooner printed off the few pages on that subject
than I wished the whole erased. I utterly disbelieve in Von Buch and de
Beaumont's views; but on the other hand, in the case of the Mauritius and
St. Jago, I cannot, perhaps unphilosophically, persuade myself that they
are merely the basal fragments of ordinary volcanoes; and therefore I
thought I would suggest the notion of a slow circumferential elevation, the
central part being left unelevated, owing to the force from below being
spent and [relieved?] in eruptions. On this view, I do not consider these
so-called craters of elevation as formed by the ejection of ashes, lava,
etc., etc., but by a peculiar kind of elevation acting round and modified
by a volcanic orifice. I wish I had left it all out; I trust that there
are in other parts of the volume more facts and less theory. The more I
reflect on volcanoes, the more I appreciate the importance of E. de
Beaumont's measurements (480/3. Elie de Beaumont's views are discussed by
Sir Charles Lyell both in the "Principles of Geology" (Edition X., 1867,
Volume I. pages 633 et seq.) and in the "Elements of Geology" (Edition
III., 1878, pages 495, 496). See also Darwin's "Geological Observations,"
Edition II., 1876, page 107.) (even if one does not believe them
implicitly) of the natural inclination of lava-streams, and even more the
importance of his view of the dikes, or unfilled fissures, in every
volcanic mountain, being the proofs and measures of the stretching and
consequent elevation which all such mountains must have undergone. I
believe he thus unintentionally explains most of his cases of lava-streams
being inclined at a greater angle than that at which they could have
flowed.

But excuse this lengthy note, and once more let me thank you for the
pleasure and encouragement you have given me--which, together with Lyell's
never-failing kindness, will help me on with South America, and, as my
books will not sell, I sometimes want such aid. I have been lately reading
with care A. d'Orbigny's work on South America (480/4. "Voyage dans
l'Amerique Meridionale--execute pendant les annees 1826-33": six volumes,
Paris, 1835-43.), and I cannot say how forcibly impressed I am with the
infinite superiority of the Lyellian school of Geology over the
continental. I always feel as if my books came half out of Lyell's brain,
and that I never acknowledge this sufficiently; nor do I know how I can
without saying so in so many words--for I have always thought that the
great merit of the "Principles" was that it altered the whole tone of one's
mind, and therefore that, when seeing a thing never seen by Lyell, one yet
saw it partially through his eyes--it would have been in some respects
better if I had done this less: but again excuse my long, and perhaps you
will think presumptuous, discussion. Enclosed is a note from Emma to Mrs.
Horner, to beg you, if you can, to give us the great pleasure of seeing you
here. We are necessarily dull here, and can offer no amusements; but the
weather is delightful, and if you could see how brightly the sun now shines
you would be tempted to come. Pray remember me most kindly to all your
family, and beg of them to accept our proposal, and give us the pleasure of
seeing them.

LETTER 481. TO C. LYELL.
Down, [September, 1844].

I was glad to get your note, and wanted to hear about your work. I have
been looking to see it advertised; it has been a long task. I had, before
your return from Scotland, determined to come up and see you; but as I had
nothing else to do in town, my courage has gradually eased off, more
especially as I have not been very well lately. We get so many invitations
here that we are grown quite dissipated, but my stomach has stood it so ill
that we are going to have a month's holidays, and go nowhere.

The subject which I was most anxious to talk over with you I have settled,
and having written sixty pages of my "S. American Geology," I am in pretty
good heart, and am determined to have very little theory and only short
descriptions. The two first chapters will, I think, be pretty good, on the
great gravel terraces and plains of Patagonia and Chili and Peru.

I am astonished and grieved over D'Orbigny's nonsense of sudden elevations.
(481/1. D'Orbigny's views are referred to by Lyell in chapter vii. of the
"Principles," Volume I. page 131. "This mud [i.e. the Pampean mud]
contains in it recent species of shells, some of them proper to brackish
water, and is believed by Mr. Darwin to be an estuary or delta deposit.
M.A. D'Orbigny, however, has advanced an hypothesis...that the agitation
and displacement of the waters of the ocean, caused by the elevation of the
Andes, gave rise to a deluge, of which this Pampean mud, which reaches
sometimes the height of 12,000 feet, is the result and monument.") I must
give you one of his cases: He finds an old beach 600 feet above sea. He
finds STILL ATTACHED to the rocks at 300 feet six species of truly littoral
shells. He finds at 20 to 30 feet above sea an immense accumulation of
chiefly littoral shells. He argues the whole 600 feet uplifted at one
blow, because the attached shells at 300 feet have not been displaced.
Therefore when the sea formed a beach at 600 feet the present littoral
shells were attached to rocks at 300 feet depth, and these same shells were
accumulating by thousands at 600 feet.

Hear this, oh Forbes. Is it not monstrous for a professed conchologist?
This is a fair specimen of his reasoning.

One of his arguments against the Pampas being a slow deposit, is that
mammifers are very seldom washed by rivers into the sea!

Because at 12,000 feet he finds the same kind of clay with that of the
Pampas he never doubts that it is contemporaneous with the Pampas
[debacle?] which accompanied the right royal salute of every volcano in the
Cordillera. What a pity these Frenchmen do not catch hold of a comet, and
return to the good old geological dramas of Burnett and Whiston. I shall
keep out of controversy, and just give my own facts. It is enough to
disgust one with Geology; though I have been much pleased with the frank,
decided, though courteous manner with which D'Orbigny disputes my
conclusions, given, unfortunately, without facts, and sometimes rashly, in
my journal.

Enough of S. America. I wish you would ask Mr. Horner (for I forgot to do
so, and am unwilling to trouble him again) whether he thinks there is too
much detail (quite independent of the merits of the book) in my volcanic
volume; as to know this would be of some real use to me. You could tell me
when we meet after York, when I will come to town. I had intended being at
York, but my courage has failed. I should much like to hear your lecture,
but still more to read it, as I think reading is always better than
hearing.

I am very glad you talk of a visit to us in the autumn if you can spare the
time. I shall be truly glad to see Mrs. Lyell and yourself here; but I
have scruples in asking any one--you know how dull we are here. Young
Hooker (481/2. Sir J.D. Hooker.) talks of coming; I wish he might meet
you,--he appears to me a most engaging young man.

I have been delighted with Prescott, of which I have read Volume I. at your
recommendation; I have just been a good deal interested with W. Taylor's
(of Norwich) "Life and Correspondence."

On your return from York I shall expect a great supply of Geological
gossip.

LETTER 482. TO C. LYELL.
[October 3rd, 1846.]

I have been much interested with Ramsay, but have no particular suggestions
to offer (482/1. "On the Denudation of South Wales and the Adjacent
Counties of England." A.C. Ramsay, "Mem. Geol. Survey Great Britain,"
Volume I., London, 1846.); I agree with all your remarks made the other
day. My final impression is that the only argument against him is to tell
him to read and re-read the "Principles," and if not then convinced to send
him to Pluto. Not but what he has well read the "Principles!" and largely
profited thereby. I know not how carefully you have read this paper, but I
think you did not mention to me that he does (page 327) (482/2. Ramsay
refers the great outlines of the country to the action of the sea in
Tertiary times. In speaking of the denudation of the coast, he says:
"Taking UNLIMITED time into account, we can conceive that any extent of
land might be so destroyed...If to this be added an EXCEEDINGLY SLOW
DEPRESSION of the land and sea bottom, the wasting process would be
materially assisted by this depression" (loc. cit., page 327).) believe
that the main part of his great denudation was effected during a vast
(almost gratuitously assumed) slow Tertiary subsidence and subsequent
Tertiary oscillating slow elevation. So our high cliff argument is
inapplicable. He seems to think his great subsidence only FAVOURABLE for
great denudation. I believe from the general nature of the off-shore sea's
bottoms that it is almost necessary; do look at two pages--page 25 of my S.
American volume--on this subject. (482/3. "Geological Observations on S.
America," 1846, page 25. "When viewing the sea-worn cliffs of Patagonia,
in some parts between 800 and 900 feet in height, and formed of horizontal
Tertiary strata, which must once have extended far seaward...a difficulty
often occurred to me, namely, how the strata could possibly have been
removed by the action of the sea at a considerable depth beneath its
surface." The cliffs of St. Helena are referred to in illustration of the
same problem; speaking of these, Darwin adds: "Now, if we had any reason
to suppose that St. Helena had, during a long period, gone on slowly
subsiding, every difficulty would be removed...I am much inclined to
suspect that we shall hereafter find in all such cases that the land with
the adjoining bed of the sea has in truth subsided..." (loc. cit., pages
25-6).)

The foundation of his views, viz., of one great sudden upheaval, strikes me
as threefold. First, to account for the great dislocations. This strikes
me as the odder, as he admits that a little northwards there were many and
some violent dislocations at many periods during the accumulation of the
Palaeozoic series. If you argue against him, allude to the cool assumption
that petty forces are conflicting: look at volcanoes; look at recurrent
similar earthquakes at same spots; look at repeatedly injected intrusive
masses. In my paper on Volcanic Phenomena in the "Geol. Transactions."
(482/4. "On the Connection of certain Volcanic Phenomena, and on the
Formation of Mountain-chains and the Effects of Continental Elevations."
"Geol. Soc. Proc." Volume II., pages 654-60, 1838; "Trans. Geol. Soc."
Volume V., pages 601-32, 1842. [Read March 7th, 1838.]) I have argued
(and Lonsdale thought well of the argument, in favour, as he remarked, of
your original doctrine) that if Hopkins' views are correct, viz., that
mountain chains are subordinate consequences to changes of level in mass,
then, as we have evidence of such horizontal movements in mass having been
slow, the foundation of mountain chains (differing from volcanoes only in
matter being injected instead of ejected) must have been slow.

Secondly, Ramsay has been influenced, I think, by his Alpine insects; but
he is wrong in thinking that there is any necessary connection of tropics
and large insects--videlicet--Galapagos Arch., under the equator. Small
insects swarm in all parts of tropics, though accompanied generally with
large ones.

Thirdly, he appears influenced by the absence of newer deposits on the old
area, blinded by the supposed necessity of sediment accumulating somewhere
near (as no doubt is true) and being PRESERVED--an example, as I think, of
the common error which I wrote to you about. The preservation of
sedimentary deposits being, as I do not doubt, the exception when they are
accumulated during periods of elevation or of stationary level, and
therefore the preservation of newer deposits would not be probable,
according to your view that Ramsay's great Palaeozoic masses were denuded,
whilst slowly rising. Do pray look at end of Chapter II., at what little I
have said on this subject in my S. American volume. (482/5. The second
chapter of the "Geological Observations" concludes with a Summary on the
Recent Elevations of the West Coast of South America, (page 53).)

I do not think you can safely argue that the whole surface was probably
denuded at same time to the level of the lateral patches of Magnesian
conglomerate.

The latter part of the paper strikes me as good, but obvious.

I shall send him my S. American volume for it is curious on how many
similar points we enter, and I modestly hope it may be a half-oz. weight
towards his conversion to better views. If he would but reject his great
sudden elevations, how sound and good he would be. I doubt whether this
letter will be worth the reading.

LETTER 483. TO C. LYELL.
Down [September 4th, 1849].

It was very good of you to write me so long a letter, which has interested
me much. I should have answered it sooner, but I have not been very well
for the few last days. Your letter has also flattered me much in many
points. I am very glad you have been thinking over the relation of
subsidence and the accumulation of deposits; it has to me removed many
great difficulties; please to observe that I have carefully abstained from
saying that sediment is not deposited during periods of elevation, but only
that it is not accumulated to sufficient thickness to withstand subsequent
beach action; on both coasts of S. America the amount of sediment
deposited, worn away, and redeposited, oftentimes must have been enormous,
but still there have been no wide formations produced: just read my
discussion (page 135 of my S. American book (483/1. See Letter 556, note.
The discussion referred to ("Geological Observations on South America,"
1846) deals with the causes of the absence of recent conchiferous deposits
on the coasts of South America.)) again with this in your mind. I never
thought of your difficulty (i.e. in relation to this discussion) of where
was the land whence the three miles of S. Wales strata were derived!
(483/2. In his classical paper "On the Denudation of South Wales and the
Adjacent Counties of England" ("Mem. Geol. Survey," Volume I., page 297,
1846), Ramsay estimates the thickness of certain Palaeozoic formations in
South Wales, and calculates the cubic contents of the strata in the area
they now occupy together with the amount removed by denudation; and he goes
on to say that it is evident that the quantity of matter employed to form
these strata was many times greater than the entire amount of solid land
they now represent above the waves. "To form, therefore, so great a
thickness, a mass of matter of nearly equal cubic contents must have been
worn by the waves and the outpourings of rivers from neighbouring lands, of
which perhaps no original trace now remains" (page 334.)) Do you not think
that it may be explained by a form of elevation which I have always
suspected to have been very common (and, indeed, had once intended getting
all facts together), viz. thus?--

(Figure 1. A line drawing of ocean bottom subsiding beside mountains and
continent rising.)

The frequency of a DEEP ocean close to a rising continent bordered with
mountains, seems to indicate these opposite movements of rising and sinking
CLOSE TOGETHER; this would easily explain the S. Wales and Eocene cases. I
will only add that I should think there would be a little more sediment
produced during subsidence than during elevation, from the resulting
outline of coast, after long period of rise. There are many points in my
volume which I should like to have discussed with you, but I will not
plague you: I should like to hear whether you think there is anything in
my conjecture on Craters of Elevation (483/3. In the "Geological
Observations on Volcanic Islands," 1844, pages 93-6, Darwin speaks of St.
Helena, St. Jago and Mauritius as being bounded by a ring of basaltic
mountains which he regards as "Craters of Elevation." While unable to
accept the theory of Elie de Beaumont and attribute their formation to a
dome-shaped elevation and consequent arching of the strata, he recognises a
"very great difficulty in admitting that these basaltic mountains are
merely the basal fragments of great volcanoes, of which the summits have
been either blown off, or, more probably, swallowed by subsidence." An
explanation of the origin and structure of these volcanic islands is
suggested which would keep them in the class of "Craters of Elevation," but
which assumes a slow elevation, during which the central hollow or platform
having been formed "not by the arching of the surface, but simply by that
part having been upraised to a less height."); I cannot possibly believe
that Saint Jago or Mauritius are the basal fragments of ordinary volcanoes;
I would sooner even admit E. de Beaumont's views than that--much as I would
sooner in my own mind in all cases follow you. Just look at page 232 in my
"S. America" for a trifling point, which, however, I remember to this day
relieved my mind of a considerable difficulty. (483/4. This probably
refers to a paragraph (page 232) "On the Eruptive Sources of the
Porphyritic Claystone and Greenstone Lavas." The opinion is put forward
that "the difficulty of tracing the streams of porphyries to their ancient
and doubtless numerous eruptive sources, may be partly explained by the
very general disturbance which the Cordillera in most parts has suffered";
but, Darwin adds, "a more specific cause may be that 'the original points
of eruption tend to become the points of injection'...On this view of there
being a tendency in the old points of eruption to become the points of
subsequent injection and disturbance, and consequently of denudation, it
ceases to be surprising that the streams of lava in the porphyritic
claystone conglomerate formation, and in other analogous cases, should most
rarely be traceable to their actual sources." The latter part of this
letter is published in "Life and Letters," I., pages 377, 378.) I remember
being struck with your discussion on the Mississippi beds in relation to
Pampas, but I should wish to read them over again; I have, however, re-lent
your work to Mrs. Rich, who, like all whom I have met, has been much
interested by it. I will stop about my own Geology. But I see I must
mention that Scrope did suggest (and I have alluded to him, page 118
(483/5. "Geological Observations," Edition II., 1876. Chapter VI. opens
with a discussion "On the Separation of the Constituent Minerals of Lava,
according to their Specific Gravities." Mr. Darwin calls attention to the
fact that Mr. P. Scrope had speculated on the subject of the separation of
the trachytic and basaltic series of lavas (page 113).), but without
distinct reference and I fear not sufficiently, though I utterly forgot
what he wrote) the separation of basalt and trachyte; but he does not
appear to have thought about the crystals, which I believe to be the
keystone of the phenomenon. I cannot but think this separation of the
molten elements has played a great part in the metamorphic rocks: how else
could the basaltic dykes have come in the great granitic districts such as
those of Brazil? What a wonderful book for labour is d'Archiac!...(483/6.
Possibly this refers to d'Archiac's "Histoire des Progres de la Geologie,"
1848.)

LETTER 484. TO LADY LYELL.
Down, Wednesday night [1849?].

I am going to beg a very very great favour of you: it is to translate one
page (and the title) of either Danish or Swedish or some such language. I
know not to whom else to apply, and I am quite dreadfully interested about
the barnacles therein described. Does Lyell know Loven, or his address and
title? for I must write to him. If Lyell knows him I would use his name as
introduction; Loven I know by name as a first-rate naturalist.

Accidentally I forgot to give you the "Footsteps," which I now return,
having ordered a copy for myself.

I sincerely hope the "Craters of Denudation" prosper; I pin my faith to
this view. (484/1. "On Craters of Denudation, with Observations on the
Structure and Growth of Volcanic Cones." "Proc. Geol. Soc." Volume VI.,
1850, pages 207-34. In a letter to Bunbury (January 17th, 1850) Lyell
wrote:..."Darwin adopts my views as to Mauritius, St. Jago, and so-called
elevation craters, which he has examined, and was puzzled with."--"Life of
Sir Charles Lyell," Volume II., page 158.)

Please tell Sir C. Lyell that outside the crater-like mountains at St.
Jago, even throughout a distance of two or three miles, there has been much
denudation of the older volcanic rocks contemporaneous with those of the
ring of mountains. (484/2. The island of St. Jago, one of the Cape de
Verde group, is fully described in the "Volcanic Islands," Chapter 1.)

I hope that you will not find the page troublesome, and that you will
forgive me asking you.

LETTER 485. TO C. LYELL.
[November 6th, 1849].

I have been deeply interested in your letter, and so far, at least, worthy
of the time it must have cost you to write it. I have not much to say. I
look at the whole question as settled. Santorin is splendid! it is
conclusive! it is perfect! (485/1. "The Gulf of Santorin, in the Grecian
Archipelago, has been for two thousand years a scene of active volcanic
operations. The largest of the three outer islands of the groups (to which
the general name of Santorin is given) is called Thera (or sometimes
Santorin), and forms more than two-thirds of the circuit of the Gulf"
("Principles of Geology," Volume II., Edition X., London, 1868, page 65).
Lyell attributed "the moderate slope of the beds in Thera...to their having
originally descended the inclined flanks of a large volcanic cone..."; he
refuted the theory of "Elevation Craters" by Leopold von Buch, which
explained the slope of the rocks in a volcanic mountain by assuming that
the inclined beds had been originally horizontal and subsequently tilted by
an explosion.) You have read Dufrenoy in a hurry, I think, and added to
the difficulty--it is the whole hill or "colline" which is composed of tuff
with cross-stratification; the central boss or "monticule" is simply
trachyte. Now, I have described one tuff crater at Galapagos (page 108)
(485/2. The pages refer to Darwin's "Geological Observations on the
Volcanic Islands, etc." 1844.) which has broken through a great solid sheet
of basalt: why should not an irregular mass of trachyte have been left in
the middle after the explosion and emission of mud which produced the
overlying tuff? Or, again, I see no difficulty in a mass of trachyte being
exposed by subsequent dislocations and bared or cleaned by rain. At
Ascension (page 40), subsequent to the last great aeriform explosion, which
has covered the country with fragments, there have been dislocations and a
large circular subsidence...Do not quote Banks' case (485/3. This refers
to Banks' Cove: see "Volcanic Islands," page 107.) (for there has been
some denudation there), but the "elliptic one" (page 105), which is 1,500
yards (three-quarters of a nautical mile) in internal diameter...and is the
very one the inclination of whose mud stream on tuff strata I measured
(before I had ever heard the name Dufrenoy) and found varying from 25 to 30
deg. Albemarle Island, instead of being a crater of elevation, as Von Buch
foolishly guessed, is formed of four great subaerial basaltic volcanoes
(page 103), of one of which you might like to know the external diameter of
the summit or crater was above three nautical miles. There are no "craters
of denudation" at Galapagos. (485/4. See Lyell "On Craters of Denudation,
with Observations on the Structure and Growth of Volcanic Cones," "Quart.
Journ. Geol. Soc." Volume VI., 1850, page 207.)