September 13, 1912] 



SCIENCE 



335 



sphere coated with electricity, except in so 

 far as either image may suggest points for 

 experimental investigation. In our igno- 

 rance of the exact mechanism of gravity it 

 is even conceivable that a particle of caloric 

 might possess mass without possessing 

 weight, though, with the possible exception 

 of the electron, nothing of the kind has yet 

 been demonstrated. In any case it would 

 appear that the mass, if any, associated 

 with a quantity of caloric must be so small 

 that we could not hope to learn much about 

 it by the direct use of the balance. 



The fundamental property of caloric, 

 that its total quantity can not be dimin- 

 ished by any known process and that it is 

 not energy but merely the vehicle or carrier 

 of energy, is most simply represented in 

 though* by imagining it to consist of some 

 indestructible form of matter. The further 

 property, that it is always generated in any 

 turbulent or irreversible process, appears 

 at first sight to conflict with this idea, be- 

 cause it is difficult to see how anything in- 

 destructible can be so easily generated. 

 When, however, we speak of caloric as be- 

 ing generated, what we really mean is that 

 it becomes associated with a material body 

 in such a way that we can observe and 

 measure its quantity by the change of state 

 produced. The calorie may have existed 

 previously in a form in which its presence 

 could not be detected. In the light of re- 

 cent discoveries we might suppose the cal- 

 orie generated to arise from the disinte- 

 gration of the atoms of matter. No doubt 

 some caloric is produced in this way, but 

 those corpuscles that are so strongly held 

 as to be incapable of detection by ordinary 

 physical methods require intense shocks to 

 diilodge them. A more probable source of 

 caloric is the ether, which, so far as we 

 know, may consist entirely of neutral cor- 

 puscles of caloric. The hypothesis of a 



continuous ether has led to great difficulties 

 in the electro-magnetic theory of light and 

 in the kinetic theory of gases. A molecular, 

 or cellular-vortex, structure appears to be 

 required. According to the researches of 

 Kelvin, Fitzgerald and Hicks, such an ether 

 can be devised to satisfy the requirements 

 of the electro-magnetic theory without 

 requiring it to possess a density many times 

 greater than that of platinum. So far as 

 the properties of caloric are concerned, a 

 neutral pair of electrons would appear to 

 constitute the simplest type of molecule, 

 though without more exact knowledge of 

 the ultimate nature of an electric charge it 

 would be impossible to predict all its prop- 

 erties. Whether an ether composed of such 

 molecules would be competent to discharge 

 satisfactorily all the onerous functions ex- 

 pected from it, may be difficult to decide, 

 but the inquiry, in its turn, would probably 

 throw light on the ultimate structure of the 

 molecule. 



Without venturing too far into the re- 

 gions of metaphysical speculation, or rea- 

 soning in vicious circles about the nature of 

 an electric charge, we may at least assert 

 with some degree of plausibility that ma- 

 terial bodies under ordinary conditions 

 probably contain a number of discrete 

 physical entities, similar in kind to X rays 

 or neutral corpuscles, which are capable of 

 acting as carriers of energy, and of pre- 

 serving the statistical equilibrium between 

 matter and radiation at any temperature in 

 virtue of their interchanges with electrons. 

 If we go a step further and identify these 

 corpuscles with the molecules of caloric, we 

 shall certainly come in conflict with some 

 of the fundamental dogmas of the kinetic 

 theory, which tries to express everything 

 in terms of energy, but the change involved 

 is mainly one of standpoint or expression. 

 The experimental facts remain the same. 



