ON THE PHYSICAL VIKW OF NATrRE. 187 



tion to it. It can be set out in tlie sUitenient that 

 wherever energy shows itself it appears as composed of 

 two factors — the intensity and the capacity factoi-s. 

 These terms, borrowed from the older theories of heat 

 and electricity, measure the quantity of energy as well as 

 the direction in which changes of energy take place: the 

 L^eneral law being that energy, in whatever form it 

 may appear, tends to go from places of higher to places 

 of lower potential or intensity. 



The characteristic feature of this most recent outcome 

 of the physical view uf natural phenomena is that it c™* 

 takes in real earnest the suggestion at which many 

 natural philosophers have independently arrived, that 

 energy is a substance quite as much as matter. .This 

 granted, it seems at least reasonable to some thinkers to 

 see how far they can get by employing the two con- 

 ceptions of matter and energy alone without adopting 

 a third something, the ether, which was introduced at 

 a time when the idea of the conservation of energy 

 had not yet been formulated.^ 



The oDt- 



' For an indication of tlie furtlier 

 development of this point of view I 

 must refer the reader to tlie chapter 

 on Photo -chemistry in Prof. Ost- 

 wald's great work ('Allg. Chemie,' 

 2nd ed., vol. ii. part 1, p. 1014, &c.) 

 " lu the interest," he says, "of a 

 conception of nature which is free 

 from hypotheses, we must ask 

 whether the assumption of that 

 medium, the ether, is unavoidable. 

 To me it does not .seem to be so. 

 If we a.sk for the cause of all dis- 



energy to be a real thing, indeed 

 the only real thing in the so-called 

 outer world, there is no need to 

 inquire for a carrier of it when we 

 find it anywhere. This enables us 

 to look upon radiant energj' as in- 

 dependently existing in sjiace. A\'e 

 have found in the gentral law of 

 intensity — i.e., in the empirical 

 fact that energy tends to equalise 

 forced changes of its den.sity in 

 space — the principle according to 

 which transmission of energy in 



placements of energy in s)>ace space necessarily takes place when 



which we can singly observe, we tliere appears aiiywheic an excess." 



find that it always consists in differ- From this and other passages of 



ences of intensity. . . . The main Prof. Ostwald's writings it seems 



point is that, having conceived ; as if ma.s8 likewise wad to lie given- 



