THE EXACT MEASUREMENT OF PHENOMENA. 317 



searches of Bunsen and Eoscoe on the chemical action of 

 light, we were absolutely devoid of any mode of measuring 

 the energy of light ; even now the methods are tedious, 

 and it is not clear that they give the energy of light so 

 much as one of its special effects. Many natural phe- 

 nomena have hardly yet been made the subject of mea- 

 surement at all, such as the intensity of sound, the phe- 

 nomena of taste and smell, the magnitude of atoms, the 

 temperature of the electric spark or of the sun's photo- 

 sphere. 



To suppose, then, that quantitative science treats only of 

 exactly measurable quantities, is a gross if it be a common 

 mistake. Whenever we are treating of an event which 

 either happens altogether or does not happen at all, we are 

 engaged with a non-quantitative phenomenon, a matter of 

 fact, not of degree ; but whenever a thing may be greater or 

 less, or twice or thrice as great as another, whenever, in short, 

 ratio enters even in the rudest manner, there science will 

 have a quantitative character. There can be little doubt, 

 indeed, that every science as it progresses will become 

 gradually more and more quantitative. Numerical pre- 

 cision is doubtless the very soul of science, as Herschel 

 said 6 , and as all natural objects exist in space, and involve 

 molecular movements, measurable in velocity and extent, 

 there is no apparent limit to the ultimate extension of 

 quantitative science. But the reader must not for a 

 moment suppose that, because we depend more and more 

 upon mathematical methods, we leave logical methods 

 behind us. Number, as I have endeavoured to show, 

 is logical in its origin, and quantity is but a development 

 of number, or is analogous thereto. 



' Preliminary Discourse on the Study of Natural Philosophy/ p. 122. 



