From Francis Galton to G. H. Darwin? 1 July 1880

D^r. Erasmus Darwin

D^r. E. Darwin's experiments on phenomena of vision are alluded to by H. Meyer in a way that implies that his readers would as a matter of course be familiar with them. In his Physiologie der Nervenfaser 238 ff (as quoted by Fechner in his Psychophysik II 485) he is describing his own peculiatires of mental imagery, and as an example of them says "When I wish to repeat Darwin's experiment (Zoonomia I.1.378)* "only the edges of the die appear to me a bright lines on a dark ground . . . "

* Sic in Fechner. but the reference does not hold for my edition, the 3^d. 1801. In this at I. p. 291, or otherwise in Part I, vol 1. Sect XVIII.6, there is an optical experiment with an imaginary cube of ivory, which might be fact to which Meyer refers but I much doubt it, recollecting well somewhere at least in his works the experiment with a die, but I cannot now find them.

From F. Galton | July 1/80

P.S. I only know of this pasage in H. Meyer through Fechners quotation of it.