To Edward Cresy   2 November [1860]¹

Dear Cresy

I return by this post D^r. 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 $\frac{1}{1400}$ 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.