308 Life ami Lrlti-rs of VntmiH (hiIIoii 



wi> call uneventful UKUally includes it lar^o simre uf tlie utmost iHissililc iiiii){i' of luiniiin pleiLsuros 

 And human p:iiiis. Thus tlio ]>hysi(i|<i<>iciil law which iii uxpi'Oj<Hed by Wcber'H fornmla is a great 

 leveller, liy preventing tlie diversities of fortune from creating by any means bo great a diversity 

 in human happiness." (pp. 11-15.) 



Galton notes how the threshold of sensation Jitters in different persons 

 and how dehcjicy t)f perception is a criterion of a superior nature. It may be 

 modifieil in the Siinie |ierson by liealth and disease, by drugs and hypnotisir). 



He notes, however, that external causes of stinnilation may be reinforced 

 by internal causes, and that external stimuli which woidd fail to exceed the 

 threshold may by aid of the imagination be magnitied to the |)roduction of a 

 just-perceptible sensation. As illustration of tliis Galton (pioted a personal 

 experience which cerUiinly deserves record in a biography for it indicates how 

 Galton worked "habitually searching for the causes and meaning of every- 

 thing that" occurred to him'." After citing Wordsworth and Tennyson as 

 cases in which the force of imagination could master their sense of the present 

 real, Galton notes that his own deafni-.'^s prevented him when seated in the 

 middle rows at a scientiHc meeting from following memt)irs read in tones 

 suitable to the audience at large. He could, however, distinguish the words 

 of the speaker if he had the unrevised proof of the memoir before 'his eyes. 

 If the speaker used words not in the proof, he f'ailetl to catch them, and if 

 he raised his eyes from the proof nothing whatever of the i-eading could be 

 undei-stood, the overtones by which words aie distinguislu^d being too faint 

 to be understood. He found that he had to approach the speaker by one 

 quarter of his distance from him to follow him'without the aid of seeing the 

 word.s. The loudness of the overtones at the two distances would be as 9 to 

 IG, and Galton concluded that his auditoiy imagination is to that of i insl 

 perceptible sound as 16 minus 9 or 7 is to 16. 



"So the effect of the imagination in this case reaches nearly half-way to the level of con- 

 sciousness. If it were a little more than twice as strong it would he able l)y itself to produce 

 an effect indistinguishable from a real sound." (p. 19.) 



He suggests that experiments as to this miglit be easily niaile with twu 

 copies of the same newspaper, a few words being altered here and there in 

 the copy to be read from. 



People growing deaf, although they cannot lip-read, appear to interpret 

 sounds better when they watch the lips of the speaker. Spectators at the 

 theatre, e.g. at the French plays, hvar better if they follow with a "Book of 

 Words." 



Whatever may be thought of Galton s explanation — the internal stimulus 

 due to the imagination — we must recognise that he discovered a most in- 

 teresting psychological problem in an experience which the bulk of men 

 would never have thought of analysing'. 



The next part of Galton's paper deals with optical continuity and the 

 just-perceptible distance between two dots. The ordinary eye is just able or 

 just unable to see two dots about a minute of angle Jisunder. Taking 



' Charles Darwin: see our p. 1. 



' A Moniewhat similar experience occurs in deciphering very bad handwriting; we find it 

 im[><«sible U> le^ul the words, until we take to imagining what the wriU'r is likely to Im' talking 

 about, and with this ossiiituucc thu eye can often realise what the iiicroglypliicii stand for. 



