176 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



modern theory of electricity, acknowledges that he "was a 

 very lively, imaginative person, and could believe in the 

 ' Arabian Nights' as easily as in the 'Encyclopedia.' ' l 

 Tyndall's "Essay on the Scientific Use of the Imagination" 2 

 has become the classic exposition of this aspect of scientific 

 discovery. 



Another feature of the act which has been called to atten- 

 tion is the unusual circumstances in which it seems to occur. 

 The history of science abounds in examples, many of them 

 doubtlessly spurious, illustrating the spontaneity of the 

 flash of insight: Archimedes discovering the principle of 

 specific gravity while bathing; Newton discovering the 

 principle of gravitation on seeing an apple fall from a tree; 

 Watt discovering the principle of the steam engine while 

 watching the tea kettle on the stove; Poincare discovering 

 the fuchsian functions while boarding an omnibus; Gauss 

 discovering the law of induction at 7 o'clock one morning 

 before arising; and so on. Hamilton's formulation of his dis- 

 covery of the Quaternions may well be quoted as descriptive 

 of a typical act of this kind. He says of these important 

 mathematical concepts, "They started into life, or light, 

 full-grown, on the 16th of October, 1843, as I was walking 

 with Lady Hamilton to Dublin, and came up to Brougham 

 Bridge. That is to say, I then and there felt the galvanic 

 circuit of thought closed, and the sparks which fell from it 

 were the fundamental equations between I, J, K; exactly such 

 as I have used them ever since. I pulled out, on the spot, a 

 pocket-book, which still exists, and made an entry, on which, 

 at the very moment, I felt that it might be worth my while to 

 expend the labours of at least ten (or it might be fifteen) 

 years to come. But then it is fair to say that this was because 

 I felt a problem to have been at that moment solved, an in- 

 tellectual want relieved, which had haunted me for at least 

 fifteen years before." 3 



1 J. H. Gladstone, Michael Faraday (London: Macmillan, 1873), p. 89. 



2 J. Tyndall, Fragments of Science (London: Longmans, Green, 1871), Vol. II. 



3 North British Review, Vol. XIV, p. 57; quoted by G. Gore, Art of Scientific Dis- 

 covery (London: Longmans, Green, 1871), p. 366. 



