20 



SCIENTIFIC THOUGHT. 



tory theory was, like the atomic theory of Dalton, driven 

 out of the country. Little was heard of it, or of Young's 

 great contribution, till it was taken up abroad, and in the 

 very place where the brilliant development by Laplace of 

 one side of Newton's suggestions had given plausibility 

 to that form of the projectile theory of light accord- 

 ing to which its material particles were supposed sub- 

 ject to attractive forces when they arrived in the 

 neighbourhood of ponderable matter. Young had 

 indeed shown that the introduction of such forces 

 could easily be dispensed with as a basis of many of 

 Laplace's calculations, and that the results could be 

 got without making use of molecular attraction. He had 

 emancipated himself from a belief in the infallibility of 

 Laplace's methods. 1 He was also one of the first to 



1 On the 20th December 1804, 

 Young presented to the Royal 

 Society his important "Memoir on 

 the Cohesion of the Fluids. " It was 

 printed in the ' Transactions' in 1 805. 

 In December 1805 Laplace read 

 before the Institute of France, and 

 subsequently published in a supple- 

 ment to the ' Me"canique celeste,' 

 his celebrated theory of capillary 

 attraction. Young bases his inves- 

 tigation entirely on the existence 

 of a surface tension, an observable 

 and measurable property ; whereas 

 Laplace falls back upon the hypo- 

 thesis of an attraction of the 

 smallest particles of matter, just 

 as he had employed the idea of 

 an attraction of matter on the 

 smallest particles of light to explain 

 atmospheric refraction according to 

 the projectile theory adopted by 

 him. In the sequel this attraction 

 is reduced to an action which is 

 insensible at sensible distances. In 

 a supplement to his memoir, which 



appeared anonymously in the first 

 number of the ' Quarterly Review ' 

 (1809), Young, evidently annoyed 

 that some of his results had been 

 reproduced without acknowledg- 

 ment (see Peacock, ' Life of Young,' 

 p. 205), reviewed the treatise of 

 Laplace "with a severity which, 

 though excessive, can hardly be 

 considered unprovoked or un- 

 merited" (ibid., p. 206). Inter 

 alia he says : ' ' The point on which 

 M. Laplace seems to rest the most 

 material part of his claim to origi- 

 nality is the deduction of all the 

 phenomena of capillary action from 

 the simple consideration of molec- 

 ular attraction. To us it does 

 not appear that the fundamental 

 principle from which he sets out 

 is at all a necessary consequence 

 of the established properties of 

 matter ; and we conceive that this 

 mode of stating the question is but 

 partially justified by the coincidence 

 of the results derived from it with 



