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 ap- 

 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 

 ifathemati- 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 Rowan Hamilton, 1 MacCullagh, Sal- 



1 Of Rowan Hamilton's dynami- ; maticians who, like Gauss, led the 

 cal " principle of varying action " I way into new channels of thought 

 I have spoken in a note to p. 231. | and succeeded in breaking through 

 William Rowan Hamilton (1805-65) ] the traditional forms of this science, 

 cannot with the same certainty as j which more than any other is ham- 

 Kant and De Tracy be claimed as , pered in its development by trans- 

 of Scotch descent. Indeed he mitted customs and habits of repre- 

 seems to belong distinctly to Ire- ' sentation. Thus, after ten years of 

 land. See Tait's article in the ! research and thought in connection 

 ' Xorth British Review,' September with the representation of extend- 

 1866, and Perceval Graves's reply in ed algebraical forms by means of 

 'Life of W. R. Hamilton' (3 vols., I the different directions in space, he 

 1882-89, vol. i. p. 5). He was one ! succeeded in establishing the fun- 

 of the few quite original mathe- damental principle of his theory of 



