Dear Cresy

Upon my life I think you must be the most good-natured man in the world. How capitally you have answered the question about the weight of water; you are as good, indeed a great deal better, than an Encyclopedia. How fortunate for me that I asked you about Hofman’s note. What a horrid blunder I should have made! But what trouble you have taken for me.—   About the measure and weights I daresay your explanation is quite right, for I looked into old and new books; but there were also most stupid misprints.—   I shall permanently keep your letter.²

As you seem a little interested about Drosera, I may mention that today I have been testing how light a weight will set a single hair moving, and I find $\frac{1}{50}$ of an inch of finest cotton thread suffices and rather shorter length (measured by micrometer) of my wife’s hair suffices; and I have sent today several inches of both to be weighed by good balance in Jermyn St.;³ and the result will show a very small fraction of a grain; so that the hairs are as sensitive to mechanical as to chemical action.— All the wild Droseras, I find, are dead for this year; so I must now write my paper and cannot try a few more experiments, as I much wished to do.

I have been much amused by your account of your conversation with Woodward and I should much like to hear you take him off. He is a very good man in his way, and his generalisations on Shells are really capital.⁴

We returned home on Saturday evening; and my girl stood the journey well; but she is very weak.

With hearty thanks | Yours very sincerely | C. Darwin