VALUE OF NUMBER OF EXPERIMENTS. 387 



The full explanation of a phenomenon requires both 

 variety and number of experiments ; variety, to enable us 

 to exclude interferences and discover causes ; and number, 

 to detect laws, general principles, and extreme and con- 

 spicuous instances. 



CHAPTER XLIL 



IMPORTANCE OF MEASUREMENTS. 



' God has made everything by weight and measure.' 



NEXT to qualitative truths themselves, their quantitative 

 relations form the essence and basis of science. Scarcely a 

 scientific research can be made without the assistance of 

 measurements. During the early periods of science, the 

 attention of mankind was limited chiefly to facts, and did 

 not largely extend to quantitative relations ; measurements 

 were then less frequently made, and those which were 

 made were comparatively crude and deficient in accuracy. 

 Even now, in a research, unless the question to be 

 solved is in itself primarily a quantitative one, measure- 

 ments are not made until the existence of the phenomena 

 themselves are ascertained. But in all the sciences, we 

 have now more or less passed the logical or qualitative 

 stage, and have entered, to a greater or less extent, into 

 the sphere of exact quantitative research. Sir William 

 Thomson, in his inaugural address, delivered in 1871, to 

 the members of the British Association, says, c Accurate 

 and minute measurement seems to the non-scientific 

 imagination a less lofty and dignified work than looking 

 for something new. But nearly all the grandest dis- 

 coveries of science have been but the rewards of accurate 



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