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Darwin Correspondence Project

From Joseph Beete Jukes   25 May 1862

Geological Survey of Ireland, | Office, 51, Stephen’s Green, Dublin, | Nenagh

May 25 1862

My dear Darwin

Many thanks for your orchid book which I received some time ago & have been carrying about with me in hopes of being able to read it.1 Hitherto I have only dipped into it and it seems excessively interesting.— Field work and reading are I find almost incompatible, after a blow on the hills, or as yesterday a climb about a mine, one has such a fatal facility for falling asleep after dinner if one attempts to read, that one is off into the land of nod without being aware of it & though I am an early bird yet I find letters, geological notes &c &c take all ones time before breakfast.—

While you are working away at the Organics I am chiefly laying the physical substratum for future observers to work on. I have however hit upon one conclusion lately which I think will interest you.—

Many of the rivers of Ireland after running over a low limestone plain with water sheds not exceeding 300 feet, escape to the sea by deep gorges thro’ hills of Slate & Old Red &c more than double that height.—

Some in the S. after running down long limestone valleys between ORS2 ridges, those valleys & ridges running straight out to the sea with same features, suddenly turn from the valleys & run through deep transverse ravines across the ridges. These latter cases I have been enabled to link on to some lateral brooks coming down from the loftier ridges on the N opposite the points where the transverse ravines commence & to show that the ravines were formed by these brooks, being commenced on a higher surface & always cutting down by running water faster than the surface of the valleys sank. Therefore it was always dry land & the valleys have been worn by atmospheric degradation alone.—3 The Limestone has in fact been dissolved; & the limestone plains & valleys have lowered & sunk down past the other rocks like glaciers sinking in their beds under a hot sun.

The other rocks have also suffered by atmospheric degradation valleys being worn in the softer parts of them.

Supposing my explanation be right in Ireland it must be applicable elsewhere. The Weald for instance, which after all is a mere flea bite compared to the denudation of the Palæozoic rocks.— I suspect that the Chalk was bared of the Tertiary rocks by marine denudation as the rock rose above the Sea, that brooks commenced to run down the chalk slopes along the courses of those which now cut ravines through the Chalk escarpments, & that those ravines have been worn by those brooks continually cutting deeper than the ground inside, that the Chalk which has been removed has been merely dissolved off the crown of the arch by atmospheric action & the hills & valleys inside worn by the rain only & the weather. Your 300,000,000 of years is not nearly enough for the denudation of the Weald by this process.4

I have sent in a paper to the Geol: Soc: Lond: on the Irish valleys w.h is to be read on June 18th.—5

I intend to be there with large maps and sections and I shall be anxious to hear if any one can pick a hole in the reasoning or give another explanation for the phenomenon

I have long been considering the “Form of Ground” as a geological problem as yet unsolved and think my idea will give us a help.—6

Agrarian outrages beginning to sprout again all over this Tipperary country.—7 Much wider emigration wanted. Only fancy! I was told by Captn. King at Silvermines yesterday, that one man had given another £80 for the possession of 6 acres of land on the hill side there: both being mere tenants at will of Lord Dunally’s.8 When the peasants buy the land in this way from one another no wonder they fancy it is their own.9

Believe me | yours very truly | J. Beete Jukes.


Jukes’s name appears on the presentation list CD drew up for Orchids (see Correspondence vol. 10, Appendix IV).
Old Red Sandstone.
Jukes was studying the mode of formation of regional drainage patterns. In his paper on the topic (Jukes 1862), Jukes introduced the concept of drainage superimposition, and propounded the idea that rivers not only excavate their valleys but adjust their courses according to underlying structures (Davies 1969, p. 330). In his history of geomorphology, G. L. Davies identified this ‘pioneer study’ as a seminal event in the ‘fluvial revival’ witnessed in Britain in the 1860s (Davies 1969, p. 330).
In Origin, pp. 285–7, CD calculated that the erosion of the Weald, at what he estimated to be a reasonable rate, would have taken 306,662,400 years. In response to criticisms in the Saturday Review, 24 December 1859, however, CD halved his estimate in the second edition of Origin, and removed the discussion altogether from the third edition. When, in the spring of 1860, CD informed Jukes of his intention to remove the passage, Jukes had sought to persuade him not to do so, expressing his conviction that the estimate ‘was not at all exagerrated’ (see Correspondence vol. 8, letter to Asa Gray, 3 April [1860], and letter to Charles Lyell, 10 April [1860]).
Jukes 1862.
In 1855, the director-general of the Geological Survey, Roderick Impey Murchison, ordered that maps be accompanied by explanatory booklets, including an account of the ‘form of ground’ or topography of the area; as director of the Irish branch of the survey, Jukes’s duties included editing these explanatory notes (Jukes 1862, p. 379). See also Davies 1969, p. 323.
Violent action by combinations formed by tenant farmers wanting reforms in the system of land tenure was on the increase in rural Ireland in the 1860s (Clark 1979, p. 211). ‘Agrarian outrage’ was a term used by the Irish constabulary to refer to any offences concerning the occupation of land (Warwick-Haller 1990, p. 22).
Henry Sadleir Prittie, third Baron Dunalley, was proprietor of 21,000 acres of land in Tipperary, Ireland (Dun 1881). Captain King has not been identified.
Jukes refers to the custom of selling one’s ‘interest’ in a holding (the ‘Ulster custom’ or ‘tenant right’). This ‘right’ had no legal status, but was a non-contractual privilege for which the tenant was usually required to obtain permission from the landlord (see Clark 1979, pp. 166–7, 180–1).


JBJ explains his theory of atmospheric denudation of Irish river valleys, to be published [as "On the river valleys in the south of Ireland", Q. J. Geol. Soc. Lond. 18 (1862): 378–403], and suggests its application to the Weald. This slow process would make the Weald far older than CD’s 300 million years.

Thanks for Orchids.

Letter details

Letter no.
Joseph Beete Jukes
Charles Robert Darwin
Sent from
Geol. Surv. Ireland, Dublin
Source of text
DAR 168: 90
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 3571,” accessed on 27 June 2019,

Also published in The Correspondence of Charles Darwin, vol. 10