ex Proceedings of the Asiatic Society of Bengal. [N.S., XV, 
footing—summarized in the two laws of thermodynamics. But 
on the ultimate nature of this energy, there was hardly set on 
foot a single enquiry. It was recognized, no doubt, that the 
intimate nature of potential energy required investigation, but it 
application of thermodynamics has suggested the discon- 
through the medium and magnetic effects associated with them. 
The questions that are pertinent and have been the subject 
matter of recent investigations, is what is it that moves in the 
‘charged’ bodies and in the medium, and what properties must 
be postulated regarding the latter? We have had, according: 
ly, the hypotheses of two fluids and one fluid to explain the 
en, to its mathematical conclusions, in Maxwell’s theory. 
Basing his views on the Faraday-Maxwell theory of stress in the 
medium, Sir O. Lodge briefly answered the first of the questions 
in his Modern Views of Electricity, by saying that it was the 
ether. Ether in static stress is according to Sir O. Lodge static 
electricity, ether in motion is current electricity, ether in vibra- 
tory motion is concerned in the propagation of the electro- 
dynamic disturbance which constitutes radiation generally, while 
ether in vortical spin is magnetism. 
This was an interesting way of bringing out the relations 
between the different aspects of the field which seemed, at the 
time, wholly justifiable, but since then important modifications 
have been called for, both on experimental and theoretical 
un For it was at once seen that the simple theory of 
Maxwell, modified in some particulars by Hertz, was capable of 
explaining only the more simple optical phenomenon of ordinary 
reflection, refraction, and double refraction but could render no 
‘Satisfactory account of metallic reflection, dispersion and aber- 
electrostatic unit, which was, at its inception, a mere matter 
of definition i 
