1908] 071 the Scientific Work of Lord Kelvin. 233 



theory and observation on the opacity of air and gases, reflexion from 

 diamond and from metals, his various attempts at elastic solid vibra- 

 tory theories of the sether, rotation of the plane of polarisation com- 

 bined with double refraction, waves on water and in dispersive media 

 with the residual disturbance they leave behind, waves raised by wind 

 or by ships, the total mass of the material universe, various theories 

 of electrons or electrions as he preferred to call them ; also much 

 regarding molecular tactic of crystals and the resulting dynamics, this 

 time on a Boscovichian foundation. The Royal Institution lecture 

 of 1900, on 'Nineteenth Century Clouds over the Dynamical Theory 

 of Heat and Light,' is also included ; these difficulties he there 

 reduces to two : the difficulty regarding the motion of matter through 

 sether, which he thinks is " not wholly dissipated," and the difficulty 

 about the frittering away of the energy of gaseous molecules among 

 their numerous periods of free vibration, which he solves in what may 

 possibly be held to be the natural way, by denying the proofs. 



Little has been said here with regard to Lord Kelvin's masterful 

 and most effective preoccupation with the development of modern 

 electric engineering, which has now almost completed the transition 

 from the age of steam to the age of electric power. In this new 

 branch of applied science, his active perception of the essentials of 

 progress assumed the form of generalship ; most of the details of pro- 

 gress naturally came from others, but he was ready always to emphasise 

 the salient pro])lems, and to acclaim, early and enthusiastically, 

 such nascent inventions as would be pertinent to their mastery. An 

 example is afforded by the emphasis with which he hailed the inven- 

 tion of the original Faure storage cell or accumulator,* which promised 

 to supply the improvements (including the subdivision of a large 

 storage battery to play the part of a step-down transformer, not yet 

 practically effective) then necessary for economical development of the 

 electric generation of power. This subject came particularly to the 

 front in his Presidential Address in 1881, at York, to the Physical 

 Section at the Jubilee Meeting of the British Association, ' On the 

 Sources of Energy in Nature available to Man for the Production of 

 Mechanical Effect,' which almost repeats the title of his early paper 

 of 1852, but is this time concerned with the practical utilisation of 

 these sources, now rapidly ripening, whereas the earlier discussion 

 related to their philosophical detection and estimation. In this 

 Address, after referring to Siemens' suggestion, three years previously, 

 of the electrical transmission at high potential of the power of 

 Niagara Falls, itself resting, as he remarks, on Joule's early experi- 

 mental discovery that in an electromagnetic engine as much as 90 

 per cent, of the energy of the driving current can be utilised, he pro- 

 ceeds to summarise his own conclusions regarding economy of trans- 



* Brit. Assoc. Report, 1881, p. 526. 



