xm.J MEASUREMENT OF PHENOMENA. 273 



forces, and is indispensable in the thermo-electric pile. 

 This balance is made by simply suspending any light rod 

 by a thin wire or thread attached to the middle point. 

 And we owe to it almost all the more delicate investiga- 

 tions in the theories of heat, electricity, and magnetism. 



Though we can now take note of the millionth of an 

 inch in space, and the millionth of a second in time, we 

 must not overlook the fact that in other operations of 

 science we are yet in the position of the Chaldseans. Not 

 many years have elapsed since the magnitudes of the 

 stars, meaning the amounts of light they send to the 

 observer's eye, were guessed at in the rudest manner, and 

 the astronomer adjudged a star to this or that order of 

 magnitude by a rough comparison with other stars of the 

 same order. To Sir John Herschel we owe an attempt 

 to introduce a uniform method of measurement and 

 expression, bearing some relation to the real photometric 

 magnitudes of the stars. 1 Previous to the researches 

 of Bunsen and Roscoe on the chemical action of light, 

 we were 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 phenomena have hardly 

 yet been made the subject of measurement at all, such 

 as the intensity of sound, the phenomena of taste and 

 smell, the magnitude of atoms, the temperature of the 

 electric spark or of the sun's photosphere. 



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 pro- 

 gresses will become gradually more and more quantita- 

 tive. Numerical precision is the soul of science, as 



1 Outlines of Astronomy, 4th ed. sect. 781, p. 52: Results of 

 Observations at the Cape of Good Hope, &c., p. 37: 



T 



