To J. F. W. Herschel 6 June 
Down Farnborough Kent
Dear Sir John Herschel
I enclose two valves of the Ibla1 done up in damp cotton; you had better put it into spirits. I hope I made it clear that I did not wish you to waste a minute of your truly valuable time, without you feel on your own account any interest in the phenomenon: I am so wholly ignorant on such points, that I did not know whether the case was of any signification. To see the blue, a thin slice must be cut off & a tolerably high single lens used to look at it, if you think it worth looking at, if not pray throw it away.2
I fear that you must find the superintendence of the Instructions3 very troublesome. Any part of mine which you think had better be struck out shall be done & I will piece it as well as I can; but if much shortening is required it will almost require rewriting & it will render necessary all one’s virtue to take that much trouble to save the Admiralty a few pounds in using smaller type. I did not put it anything for the mere purpose of swelling mine.
Believe me | Yours sincerely | C. Darwin To Sir J. W. Herschel Bart.
Sends two valves of Ibla.
In his chapter [for Manual, Collected papers 1: 227–50], he will strike out any part that JFWH wants struck out, but if much shortening is required it will need rewriting.
Please cite as
Darwin Correspondence Project, “Letter no. 1183,” accessed on 4 May 2016, http://www.darwinproject.ac.uk/DCP-LETT-1183