274 



SCIENTIFIC THOUGHT. 



longs to the second half of the century, and is centred in 

 the two names of William Thomson (Lord Kelvin) and 

 James Clerk Maxwell, who may be said to have jointly 

 revolutionised natural philosophy. It began with the apr 

 pearance of George Stokes's and William Thomson's im- 

 portant contributions to mathematical physics, and with 

 the publication of that suggestive and stimulating but 

 unfortunately unfinished work by Thomson and Tait on 

 Natural Philosophy. It was represented to the fullest 

 extent in Clerk Maxwell's activity in the Cavendish 

 Laboratory at Cambridge. But the consideration of this 

 subject belongs to a later chapter of the present work, 

 and is only mentioned here in connection with the intel- 

 lectual intercourse and exchange which has existed all 

 through this century between the invigorating spirit of the 

 north and the more conservative spirit of the southern 

 39. portion of the island. Besides Scotland another centre 

 Mathemati- the Dublin School has gained European renown 



cal School. 



through a series of mathematical labours of the highest 

 importance, some of them of an originality hardly yet 

 sufficiently recognised.- This school is represented by 

 the names of Eowan Hamilton, 1 MacCullagh, Sal- 



1 Of Rowan Hamilton's dynami- 

 cal " principle of varying action " 

 I have spoken in a note to p. 231. 

 William Rowan Hamilton (1805-65) 

 cannot with the same certainty as 

 Kant and De Tracy be claimed as 

 of Scotch descent. Indeed he 

 seems to belong distinctly to Ire- 

 land. See Tait's article in the 

 ' North British Review,' September 

 1866, and Perceval Graves's reply in 

 'Life of W. R. Hamilton' (3 vols., 

 1882-89, vol. i. p. 5). He was one 

 of the few quite original mathe- 



maticians who, like Gauss, led the 

 way into new channels of thought 

 and succeeded in breaking through 

 the traditional forms of this science, 

 which more than any other is ham- 

 pered in its development by trans- 

 mitted customs and habits of repre- 

 sentation. Thus, after ten years of 

 research and thought in connection 

 with the representation of extend- 

 ed algebraical forms by means of 

 the different directions in space, he 

 succeeded in establishing the fun- 

 damental principle of his theory of 



