In a letter to "Lady Mary", written from the Hotel Cherbourg-Vichy, Allier, France on 7 June 1880, Francis Galton alludes to his work on people who produced mental maps of numbers, which he called "number forms" or "visualized numerals": "Your note has just reached me at Vichy, where my wife has been banished on account of health for 3 weeks, so, amongst other pleasures, we lost that of being at the R. Soc. [Royal Society] conversazione where I would have been very glad to have heard [M?] Martineau's account. I hope you have not lost their first separate pencil sketches. They would be of very great interest to me, because it is rare that the shape of the number-form agrees closely in two relations. The hereditary tendency to form some forms is very strong, and that to make a particular form is independent, so that there is a double or compound chance against a particular form being inherited. I am still collecting these cases, wherever they are exceptional, for although my memoir with about 35 illustrations is in type and done with (though not yet published) I suppose that I shall write a book before long about mental imagery general[l]y and sh[oul]d of course revise and add to what has been published before." He continues: "Just now I am busy in Hallucinations. It is a most curious subject. I feel sure that much more may be theorized about their origin than has yet been done. ..."

1 unknown (1 sheet)

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