PHYSICS. 579 



stantaneously from IS'ewton's law of motion (usually stated as three), on 

 the one hand, and a denial of action at a distance on the other, thus : "If 

 A does work on B it exerts force on it through a certain distance; but 

 (Newton's law) B exerts an equal opposite force and (being in contact) • 

 through exactly the same distance ; hence B does an equal opposite 

 amount of work or gains the energy which A loses. The stress between 

 A and B is the means of transferring energy from A to B, directly mo- 

 tion takes place in the sense AB. And the energy cannot jnmp from 

 A to B ; it is transferred across their point of contact, and by hypothesis, 

 their 'contact' is absolute; there is no intervening gaj), microscopic, 

 molecular, or otherwise. The energy may be watched at every instant. 

 Its existence is continuous; it possesses identity." Obviously A and B 

 cannot be " pieces of matter" in the ordinary sense, since then they 

 cannot be in contact. If A and M be contiguous material molecules, 

 energy may be transferred from A to M, but not directly ; A cannot act 

 on M, cannot do work on it, because of the intervening gap. A can 

 transfer its energy to B, B to C, r.o D, and so on, handing on the en- 

 ergy to L, which is in contact with, and can act on, M, doing work on it 

 and giving up to it the energy lost by A. A, B, C, &c., are supposed 

 to be successive portions of the perfectly continuous space-filling me- 

 dium — aether. The distinction between potential and kinetic energy is 

 then discussed, and the conclusion stated : (1) Energy cannot be trans- 

 ferred without being transformed ; nor conversely can it be transformed 

 without being transferred ; and (2) it always transforms itself from 

 kinetic to potential or vice versa. "When A does work on B, energy 

 is transferred from A to B ; if the energy lost by A is kinetic, that 

 gained by B is potential ; if, on the other hand, A loses potential then 

 B gains kinetic energy." Hence " the common mode of treating a fall- 

 ing weight, saying that its energy gradually transforms itself from 

 potential to kinetic, but remains in tbe stone all the time, is, strictly 

 speaking, nonsense. The fact is the stone never had any potential en- 

 ergy; no rigid body can have any; the gravitation medium had it, how- 

 ever, and kept on transferring it to the stone all the time it was descend- 

 ing." Change of form is therefore necessary and universal whenever 

 energy is transferred, /. c, whenever any kind of activity is exhibited 

 by any known kind of material existence. {Phil. Mag., June, 1885, V, 

 XIX, 482.) 



Groshans has announced a new law connecting the boiling points and 

 densities of substances with tbeir atomic composition, which law he calls 

 "The law of Density-numbers." These density numbers form a new 

 class of constants, and are attributes of the elements; they are whole 

 numbers, and each element i)Oss('sses only one, though two or more 

 elements may possess the same number. They increase with tbe atomic 

 weights, but are not proportional to them. From the values thus far 

 obtained, the author suggests the hypothesis that carbon, oxygen, and 

 hydrogen are simple bodies, the other elements being compounds of 



