238 Life ami LHtern of Francis Galton 



The reader of the jmper will certAinly realise — probably for the first time 

 — how very varied is the power of mental imtigery among individuals. But 

 unless the reader is very faiuiliar with the process of 'ranking' he is unlikely 

 t4» extract at once frotn that system such results a« that : 1 2 per cent, of persons 

 see the mental inuige as vividly iis the real thing, 12 per cent, only recall 

 c<.ilours by a special effort for each, and more than (J per cent, have a larger field 

 of mental than of normal view, i.e. can see more than a hemisphere, all the 

 fjices of a die at once or the three walls of a room, and even the fourth 

 simultaneously by an effort. It may be doubted whether the ranking scheme 

 wjis best adapted to attract attention to a most interesting investigation. 

 The paper concludes with a few observations on "visualised numerals." 



I had frecjuently been puzzled by a number of lantern slides in the 

 (iaitoniatta, which besides giving various phenomena associated with mental 

 imagery provided illustrations of liuslnuan, Mskinio and palaeolithic draw- 

 ings and carvings. They undoui)tedly belonged to some public lecture, but 

 there was nothing in the three lists of papers prepared by Galton hini.solf to 

 indiaite that this lecture wiis ever published, nor was tliere any statement 

 on p. 339 of the Inquines into liuruan Faculty to say that the "1880 

 Mental Imagery. Forfiw/hth/ liexnew; Mind" referred to practically distinct 

 pa|)ers. They are, however, distinct, and although the F<>r(iti(//itli/^ })aper, en- 

 titled "Mental Imagery," does not cover the whole ground of the lantern 

 slides, there is little doubt that it contains a great deal of the substanee of 

 the lecture to which they belonged. The lecture wjis certainly one on ''Mental 

 Imagery," and, although it was not published in extcnm, the Fortnujhlly 

 probably containetl the substance of it. There is little doubt that both slides 

 and Forlniijhtly paper deal with the nmtter of Galton's popular lecture at 

 the Swansea Meeting of the British Association in 1880. According to L. G.'s 

 Record that meeting was attended by Galton and his wife. Mrs Galton makes 

 no reference to the lecture, nor have I discovered any manuscript of it in the 

 Galtoniana. It is jwssible that it was needful to cut out a good deal of 

 the material of the lectm'o from the Fortniyhtly article as it would not be 

 intelligible without illastrations. 



The paper commences with what Galton himself calls vague physiological 

 considerations concerning tlie difference between a sensation received by the 

 optic nerve and transmitted to the brain, and a mental image where the 

 secjuence of events would occur in the reverse order, there being tlie propa- 

 gation of a central impulse from the brain towaids the optic nerve. This 

 reverse process can be so vigorous that the mental image is vivid, and may 

 in certain cases amount to a hallucination. The.se considerations 



"justify us in ascril)iii)jj the inarkod diffen-nccs in tlie quality, an wfll i\a the vivi(liu«a, of the 

 mental iuiagerj" of ditlerent persons, U) the various (Jegre<?H in which the several links of a long 

 nervous chain are apt to Ik? afltjcted." (p. 313.) 



Galton states that 

 "his purpose is to point out the coniiitioiiH under which mental imager}' a.s alwve defined is 



' FortnigMy Review, Vol. xxvui, N.S. pp. 312-24, Septeml>«!r, 1880. The Afind paper is 

 entitled "Statistics of Mental Imagery." {Uril. Amoc. llejxirl, 18H0, p. Ixxviii.) 



