Reduced to its lowest terms, Dr. Larmor's conception of the ether is that of a 'rotationally elastic medium.'[76] In other words, it resists being turned round an axis. The forces continually acting upon it are nevertheless of a gyratory nature; and hence arise strains, betrayed to our apprehension by electrical manifestations. Each 'electron' is held to be the nucleus of some kind of distortion or displacement,[77] and carries with it, as it moves, a field of force. Out of these 'point charges' material atoms are variously built up. They are 'structures in the ether,' encompassed by 'atmospheres of ethereal strain,' not--as they were formerly taken to be--'small bodies exerting direct action at a distance on other atoms according to extraneous laws of force.'[78] Obviously the new view brings to the front extremely subtle questions regarding the nature of 'dynamical transmission'[79]--what the propagation of energy essentially consists in, and by what mechanism it is effected; and they are, for the present, unanswerable. Electricity is, on the theory we are attempting to sketch, positive or negative according to the direction of the originating strain. A positive electron might be imagined to resemble a spiral nebula of the right-handed sort, a negative one a left-handed spiral, or _vice versâ_. The analogy is, perhaps, fanciful; yet it helps towards obtaining a mental picture of objects which, insignificant and elusive though they appear, may be the initials and ultimates of this strange world. The forces, at any rate, by which it is at present kept going are evoked _ad libitum_ by the pioneers of modern research from the ethereal plenum. The actualities of matter are potentialities in the ether. 'All mass,' in Professor J. J. Thomson's opinion, 'is mass of the ether, all momentum, momentum of the ether, and all kinetic energy, kinetic energy of the ether.[80] Only if this be so,' he adds, 'the density of the ether must be immensely greater than that of any known substance.'