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Darwin Correspondence Project

To Edward Cresy   2 November [1860]1

15 Marine Parade, Eastbourne

Nov: 2nd.

Dear Cresy

I return by this post Dr. Taylor’s pamphlet which is very interesting.—2

This morning I vowed to myself that I would give you no more trouble; this evening I break my vow! Do read over Hofman’s note,3 it seems to me clear that he asserts that he has easily distinguished 0.002 of milligram of iodine and this equals, as I make out, 3/100,000 of a grain! Whereas Taylor, in your copy, speaks of only 11400 of a grain.4 Can you understand this? Pray do not trouble Hofman again, for I shall see him in course of early winter. Now I am on weights, can you assist me in another point. I have used ordinary apothecary measures (which I shall state in my paper), viz, fluid oz. divided into 8 drachms and each drachm into 60 minims,—so that each oz. contains 480 minims.5 But when I looked into such books as I possessed I found the most ridiculous discrepancies and misprints of weight of one such oz. of distilled water. I applied to good and clever druggist and he says positively one such oz. weighs 437.5 grains and this agreed with one of my printed authorities; so I have provisionally used it in calculating proportions. Can you anyhow aid me in telling me whether this is correct?6

God forgive me for being so troublesome, and believe me, | Yours very sincerely | C. Darwin

Please return Hofman’s note.


The letter was written in the evening, after the preceding letter was posted.
Taylor 1860. See preceding letter.
Letter from A. W. von Hofmann to Edward Cresy, 27 October 1860. See preceding letter.
Taylor 1860. There is a note on this pamphlet in DAR 60.1: 69 listing the amounts of arsenic and antimony that could be detected.
A note giving these calculations and apparently subsequent emendations is in DAR 60.1: 70.


Discusses pamphlet by A. S. Taylor

and note by A. W. v. Hofmann concerning iodine solution.

Letter details

Letter no.
Charles Robert Darwin
Edward Cresy
Sent from
Source of text
DAR 143
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 2974,” accessed on 26 June 2017,

Also published in The Correspondence of Charles Darwin, vol. 8