SOME VIEWS ON LORD KELVIN'S WORK 427 



scheme representing the chemical elements as arranged in 

 Mendelejeff's table {Physical Review, April 191 2). 



The "Aepinus Atomised" article of 1901 illustrates a host 

 of electrical actions and electrical properties of solids, liquids, 

 and gases, such as electrolysis, chemical affinity, heat of com- 

 bination, electric conductivity of solids and its changes with 

 temperature, specific inductive capacity, very much as on other 

 electron theories. Combinations of atoms in various configu- 

 rations are obtained to account for crystalline formations and 

 for the electrical properties of crystals. The results of experi- 

 mental investigations on Radioactivity, which Lord Kelvin 

 followed with the keenest interest, prompted him to visualise 

 the actions within radioactive bodies by constructing model 

 atoms having the properties of radium and polonium, and to 

 extend his system of atoms and electrons to account for the 

 various types of rays which experiment revealed. A typical 

 paper of Lord Kelvin's belonging to this group is the one 

 entitled "Electric Insulation in 'Vacuum,'" in which he com- 

 pares the force required to pluck an electron from its atom 

 with the breaking weight of the strongest steel. The bearing 

 of this work of atom construction on the explanation of 

 spectroscopic series, and of the general mechanism of radia- 

 tion, is discussed fully in Lord Kelvin's latest completed paper 

 " On the Motions of Ether produced by Collisions of Atoms or 

 Molecules containing or not containing Electrons" {Phil. Mag., 

 September 1907). A clear statement given in this paper of Lord 

 Kelvin's views regarding radiation is of importance in relation to 

 the extensions referred to in the following pages : " The pulses 

 described in §§ 11, 12, as due merely to mutual collisions between 

 ponderable atoms (without consideration of electrons whether 

 present or not), constitute a kind of motion in the ether, which, 

 if intense enough to produce visible light, would, when analysed 

 by the spectroscope, show a continuous spectrum without the 

 bright lines, which, when seen, prove the existence of long-con- 

 tinued trains of sinusoidal vibrations of particles of ether in the 

 eye perceiving them, and therefore also in the source, and in 

 all the ether between the source and the eye. On the other 

 hand, the vibrations of electrons referred to in § 13 would, if 

 intense enough, produce bright lines in the spectrum." The 

 main difference between Lord Kelvin's views and current ideas 

 regarding atomic structure lies in his choice of static con- 



