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Darwin Correspondence Project

From Horace Darwin   17 August 1874

1 Pier Road | Erith

Aug 17th. 74

Dear Mother

Will you tell Father that I have hunted in the only two book’s about the steam engine wh. I know of and can find nothing of any good. I had a talk with the Manager Mr Moberly, & he said that feed water heaters did not get so much choked up as the boiler, but I do’nt think this shews so very much, because the only kind of deposit wh. is much harm, I believe, is a solid insoluable crust wh. coveres the inside of the boiler; and the feed water heater may precipitate the carbonate of lime, as powder and not as “scale” as it is called; and if it does the precipitate would go into the boiler and might get turnde into the scale there.1 What makes me think that this is possible is that there is a patent for preventing the scale by sending an electrical current from the water to the metal of the boiler, but whether this acts I do’nt know, we are trying it at the works but the boiler has not been cleaned out since it was put up, so they dont know how it works; if it does answer it shows that there is something very odd about it, so one can’t tell for certain. Mr. Moberly also said that he thought that 100o Far.2 would precipitate very little of the Car. of lime; I will get another talk with him. All he said only applied to fresh warter heaters. I looked at Watts Dictionary of Chemistry & found a good deal about it under. Water-Solution— gaves absorption of—Carbonate of Calcium—Carbonic anhydride— water does disolve less Carbonic acid the hotter it gets.3

I want to hear very much what answer Murray gives.4

Yours affec son | H Darwin


Horace had recently begun a three-year apprenticeship at Easton and Anderson, engineers, of Erith, Kent (ODNB). He refers to Charles Henry Moberly. Feed-water heaters preheat the water before it goes into the main boiler.
100oF: 38oC.
Horace may refer to John Murray, CD’s publisher.


ODNB: Oxford dictionary of national biography: from the earliest times to the year 2000. (Revised edition.) Edited by H. C. G. Matthew and Brian Harrison. 60 vols. and index. Oxford: Oxford University Press. 2004.

Watts, Henry. 1872–4. A dictionary of chemistry and the allied branches of other sciences. 2d edition. 5 vols. London: Longman, Green, & Co.


The occurrence and prevention of scale in boilers.

Anxious to hear Murray’s reply [to CD’s letter 9598].

Letter details

Letter no.
Horace Darwin
Emma Wedgwood/Emma Darwin
Sent from
Source of text
DAR 162: 70
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9603,” accessed on 27 October 2021,

Also published in The Correspondence of Charles Darwin, vol. 22