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Darwin Correspondence Project

From Daniel Mackintosh   21 November 1880

36 Whitford Road | Tranmere, | Birkenhead,

21st Nov. 1880.

Dear Sir,

I am much obliged by the receipt of your kind letter of the 13th. I admit I was writing rather carelessly when I spoke of earthquakes as a geological cause in my last letter.1

With regard to changes in the level of the sea, the existence of shelly beach deposits at between about 1,100 and 1350 f. in mountain districts at a considerable distance from each other (as for instance, the Wicklow hills, Moel Tryfan, S. of Minera (Denbyshire) and above Macclesfield) would certainly seem to be better explained by the surface of the sea being higher than by the land being lower; but I have found it better not to complicate the subject by entering much into this question.2

I have not read of any geologist having noticed the shattered rocks under the drift of Moel Tryfan excepting yourself.3 I have seen them twice, at different levels in the new quarries, and you must have seen them in the old at a lower level. I look upon them as the most remarkable phenomon connected with Moel Tryfan, excepting the discovery of sea-shells.

With many thanks, | I am Dear Sir, | Your obliged & faithful Servant, | D. Mackintosh.

P.S. In the new or upper quarry sections, there is clear evidence of the floating ice having come from the N.W. or from the N. of Ireland.

Footnotes

Mackintosh cited CD’s paper on the drift deposits on Moel Tryfan (‘Ancient glaciers of Caernarvonshire’) in Mackintosh 1881, p. 352.

Bibliography

‘Ancient glaciers of Caernarvonshire’: Notes on the effects produced by the ancient glaciers of Caernarvonshire, and on the boulders transported by floating ice. By Charles Darwin. Philosophical Magazine 3d ser. 21 (1842): 180–8. [Shorter publications, pp. 140–7.]

Mackintosh, Daniel. 1881. On the precise mode of accumulation and derivation of the Moel-Tryfan shelly deposits; on the discovery of similar high-level deposits along the eastern slopes of the Welsh mountains; and on the existence of drift-zones, showing probable variations in the rate of submergence. [Read 27 April 1881.] Quarterly Journal of the Geological Society of London 37: 351–69.

Summary

The use of earthquakes as a geological cause in his previous letter was careless.

Shelly beach deposits over considerable distance from Ireland to Scotland seem better explained by high sea-level than low land.

Only CD seems to have reported shattered rocks under the Moel Tryfan drift.

Letter details

Letter no.
DCP-LETT-12836
From
Daniel Mackintosh
To
Charles Robert Darwin
Sent from
Tranmere
Source of text
DAR 171: 11
Physical description
ALS 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 12836,” accessed on 28 March 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-12836.xml

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