1008] on the Scientific Work of Lord Kelvin. 231 



trolled by Solar influence ; but here the problem has proved not to 

 be so feasible, the definite periodic components being so mixed up 

 with the erratic results of meteorological instabilities that not much 

 has yet come out of the effort. 



In later years Helmholtz paid many holiday visits at Largs, and 

 enjoyed the yachting expeditions, which provided a refuge for him 

 from the attacks of hay fever. In 1871, the two friends studied the 

 theory of waves which Thomson " loved to treat as a kind of race 

 between us." It was shortly before that Thomson had broken new 

 ground suggested by observations from his becalmed yacht, on the 

 theory of capillary ripples, and on the waves produced by wind and 

 current, treated in two letters to Tait intended for the Royal Society 

 of Edinburgh. In later years the latter subject Avas discussed in 

 much more detail and developed in new directions by Helmholtz, 

 with a view^ to meteorological atmospheric applications.* 



On board the yacht, Helmholtz reports f that " It was all very 

 friendly and unconstrained. Thomson presumed so much on his 

 intimacy with them that he always carried his mathematical notebook 

 about with him, and would begin to calculate in the midst of the 

 company if anything occurred to him, Avliich was treated with a 

 certain awe by the party. How would it be, if I accustomed the 

 Berliners to the same proceeding ? . . ." 



In 1884 Sir W. Thomson delivered the well-known course of 

 lectures on ' Molecular Dynamics and the Wave Theory of Light,' at 

 Johns Hopkins University, Baltimore, after attending the meeting of 

 the British Association at Montreal. The papyrograph unre vised 

 report, issued in December 1884, by Mr. A. S. Hathaway, may justly 

 be said to have reawakened, or at any rate strongly intensified, interest 

 in the ultimate form of the problem of tether and radiation, both in 

 this country and abroad. It seems fair to say also that the interest 

 and value of the lectures arose largely from the unpreparedness of 

 their author. As his audience of American physicists fed him from 

 day to day with the more recent experimental and theoretical results 

 relating to selective absorption, which were largely new to him, they had 

 before them the spectacle, on which Helmholtz had laid stress, of one 

 of the great minds of the century struggling with fresh knowledge and 

 trying to assimilate it into his scheme of physical explanation, calling 

 up all his vivid store of imagery and analogy to aid. His auditors 

 at the time, and his readers afterwards, thus must have considered the 

 lacunaB and difficulties as their own personal problems in which they 

 were assisting. Perhaps no exposition in physical science so vivid and 

 tempting has ever been })ublished ; and for many years afterwards 

 scientific activity in these subjects was strongly tinged by the Balti- 



* Cf. Baltimore Lectures, Appendix G, and Prof. Lamb's Hydrodynamics, 

 t Life, p. 287. 



