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Darwin Correspondence Project

From J. D. Hooker   4 August 1856

Aug 4th. 1856

Dear Darwin

Thanks for Lyells letters which are very tough reading—1 I certainly enjoy all the freedom of motion in vacuo as far as the Geological difficulties are concerned, not because I would underrate their magnitude & importance, but because we really seem to know so little about them. What the deuce are these Eocenes, Miocenes, & Pleiocenes but shadows of Geological phenomena, whose substance (in so far as that substance is the reconstruction of the Earths surface at the period) we really appear to know nothing whatever about.

If Snowdon has gone up 3000 feet since the Glacial epoch & the sea has left no trace of its presence over the thousands of square miles but the wretched little shell beds that you might almost pocket in a visit, it would really seem that we have but fixed the hazy edge of the shadow of Geological change during the period of existing species As an outside barbarian I have always thought that Geologists make too much out of their facts: though I do not think they can magnify the importance of the facts I think they can make too much of them. Have you read Austen on the possible extension of the coal fields?2 that does appear to me outgeologizing Geology, with a vengeance

My object in now writing is not to discuss Lyells letters wh. I have not digested at all, but to tell you that two of my New Zealand Epacrideæ that I had thought new, are the same with Tasmanians: both are mountain Tasmanian; & one truly Alpine, both in Tasm. & N. Zealand. This prevalence of scarce Alpines common to N.Z. & V.D L. coupled with the total absence of Eucalypti & any Myrtaceæ & Acaciæ or any Legum: in common, is to my mind a damning evidence against migration.3 The mere fact that little scarce alpine things with no apparent means of transport should be common to the two tracts of land, whilst, hundreds of shrubs & trees & Composites that clothe Tasmania & Australia like a garment (I especially allude to Acacias, Epacrid & Eucalypti & other Myrtaceæ) which have, some, millions of minute seeds, wafted aloft, others good hard seeds for transport of other kinds, others pappus & viscid seeds & when you consider that these are not only in abundance of individuals but in point of number of the genera & species they belong to dominant families of Tasmania & Australia—I do think that to call for migration for those rarer & more local plants that have got across is against all facts & all philosophy & is to me the most inconceivably gratuitous assumption, being further unsupported by a single fact of special adaptation to migration in the plants themselves.4

I am quite ready to admit the gigantic difficulties in the way of Continental Extension, & I also admit that it does not explain all the facts & is no more than an idea perhaps; but it does not fly in the face of known facts in the history of distribution & the geological arguments against it are of no proved value. The Continental Extension may be a retrograde step, but it is no harm done, whereas the migration strikes at the root of logical induction from known facts in distribution.

This is all very fine talking. I shall certainly have another shy at the subject when Fl. Tasmania is done.5

To my mind the matter stands thus;—there are facts against migration which you & every one acknowledge: & there are arguments (not facts) against the theory of Continental Extension, whose full value you do not yourself know & upon which no two Geologists agree. Under these circumstances I reject migration, & hesitatingly accept continental Extension, waiting for more light upon the subject

This is the aspect the question bears to my eyes at present. I grant that it may be susceptible of huge modifications— The difference between us lies in this—that you are more of a Geologist than Botanist & feel the real weight of the Geolog. objections. I am no Geologist at all & enjoy the aforesaid freedom of motion.

With regard to Lyells letters I doubt if the throws any real light upon the grand question of continental extension by niggling (as Sedgwick seems to have it)6 at local subsidences. If there is, as you seem to show, a relation between lofty volcanic Mts & ocean,7 & between lofty non volcanic Mts & continents, we must seek some explanation of so grand a generalization in the operation of cosmical causes & the first that occurs is hydrostatic pressure. now if one had only the gift of the gab, & cheek enough, one might keep the Geolog. Soc. in extasy with speculations of that description. Central heat would be a trifle to it.

Your argument about great Mammalia is good, but cuts both ways, why did they not migrate if the Java & Borneo &c &c &c beasts are the same—& again are not the means of destruction of large beasts on Islands tenfold greater than of small.? want of food in case of Carnivora—

I think I can quite understand what Lyell means by saying that, your or vestigial notions will invalidate specific centres;8 & that it resides in this, that you will have to hedge about your theory with (what will appear to most people) to be gratuitous assumptions to prevent their or your quoting change of form for every centre. Thus, if Ægilops & wheat are transmutations & the duration of Ægilops as a species be 3 geological epochs (A. B. C.) & its spread in area to be the Northern hemisphere, you may have physical causes causing its transmutation during A & C. only—& at 3 independent spots X, Y. Z. in the area— You thus annihilate both centres & time— My strongest argument against transmutation are 1) that the vegetable world does not appear in the confusion I should expect it to be in, were transmutation the law. 2) that I do not find that repetition of species, or of forms, under closely similar physical conditions, that I should have expected transmutation to have effected. If I accept transmutation I am prepared to give up much specific centralization as an inevitable consequence.— This shakes Geological systems to the foundation & geographical distribution too.

But I must break off. I return Lyell’s letters, they are very suggestive but I do not see that they much touch the question— What do you think of Tyndall’s explanation of Cleavage?9

Ever Yrs | J D Hooker

CD annotations

0.3 Dear … vengeance. 2.9] crossed pencil
7.1 This … time— 10.9] crossed pencil
10.9 1) … law. 10.11] ‘no’ added pencil
10.11 2) … effected. 10.13] ‘no’ added pencil
10.13 If … Hooker 12.1] crossed pencil

Footnotes

Godwin-Austen 1856 was read at a meeting of the Geological Society of London on 30 May 1855. Robert Alfred Cloyne Godwin-Austen concluded that geological evidence was sufficient ‘to admit of the restoration of the original surfaces which supported the coal-vegetation’ in Europe (pp. 72–3) and that there were strong a priori reasons to suppose there was a band of coal measures along the line of the valley of the Thames (p. 73).
In Natural selection, p. 564, n. 2, CD suggested that seeds carried on boulders transported by icebergs might explain alpine plants common to New Zealand and Van Diemen’s Land (Tasmania).
In J. D. Hooker 1853–5, 1: xix, Hooker noted: ‘The idea of transportation by aerial or oceanic currents cannot be entertained, as the seeds of neither [Edwardsia grandiflora nor Oxalis magellanica] could stand exposure to the salt water, and they are too heavy to be borne in the air.’ He also commented that the plants showed no apparent adaptations for transportal (p. xxi).
Hooker had been publishing his Flora Tasmaniæ in parts since 1855 (see Wiltshear 1913). The work was completed in 1860 (J. D. Hooker 1855[–60]).
An allusion to the transmutationist views expressed in Vestiges of the natural history of creation ([Chambers] 1844). See letter to J. D. Hooker, 30 July [1856].
In a lecture delivered at the Royal Institution on 6 June 1856 (Tyndall 1856), John Tyndall discussed cleavage in rocks and other solids with the intention of distinguishing between cleavage due to crystalline action and cleavage caused by mechanical agencies. The latter, argued Tyndall, was primarily the result of compression. CD had long been interested in the phenomena of cleavage and foliation (see Correspondence vols. 3, 4, and 5).

Summary

JDH’s arguments against transmutation: 1. Plants do not show the confusion he would expect; 2. Under clearly similar physical conditions we do not find same species.

JDH’s argument against migration: commonality of alpine species. Believes migration opposes facts of botanical distribution in Van Diemen’s Land and New Zealand; prefers continental extension theory.

Letter details

Letter no.
DCP-LETT-1937
From
Joseph Dalton Hooker
To
Charles Robert Darwin
Sent from
unstated
Source of text
DAR 100: 100–4
Physical description
10pp †

Please cite as

Darwin Correspondence Project, “Letter no. 1937,” accessed on 20 March 2019, http://www.darwinproject.ac.uk/DCP-LETT-1937

Also published in The Correspondence of Charles Darwin, vol. 6

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