To R. F. Cooke   28 May [1871]¹

My dear Sir

I am greatly obliged for all the information about printing Photos. The Heliotype seems considerably the cheapest, & I think I could not do better than try one set of Plates.² What do you think? I shall come to London in 6 or 7 weeks, possibly rather sooner, & then I will arrange with M^r. Rejlander about sending the negatives of some.—³ Will you take the trouble, if you agree with me, to write one line to this effect to M^ess Edwards & Kidd.⁴ It will be very important for my work to have as good illustrations as possible, & of course I must be as careful as I can about cost.

There is one other element to ascertain, & to inform me, viz the cost of M^r Coopers engraving: he has done two & is doing a third: they are excellently done, but some of my friends tell me that they think, photos w^d be better than even fac simile engravings, in as much as the former are a guarantee of absolute accuracy.⁵ What must be done about lettering the Photos.? I cannot possibly tell the number of each plate till book nearly ready, & then there will be great delay in printing them.— Could they be numbered by Hand?

Kindly aid me by thinking over the points in this note, & believe me | Your’s very faithfully | Ch. Darwin

P.S. A naturalist to my surprise applied to me the other day to translate into Sweedish my old Journal of Researches:⁶ I told him that I believed M^r Murray would, at my request, supply stereotypes of the few cuts in it, at little more than cost price. Will he so far oblige me.?—