124 WHAT IS SCIENCE? 



desire to weigh. This result is an experimental fact 

 which could not have been predicted without experi- 

 mental inquiry. And the result is true, not only for the 

 measurable property weight, but for all properties measur- 

 able by the process that is applicable to weight. Once 

 more we see how much simpler and more conveniently 

 things turn out than we have really any right to expect ; 

 measurement would have been a much more complex 

 business if the law that has just been stated were not 

 always true. 



DERIVED MEASUREMENT 



Measurement, it was said on p. no, is the assignment 

 of numbers (or, as we say now, numerals) to represent 

 properties. We have now considered one way in which 

 this assignment is made, and have brought to light the 

 laws which must be true if this way is to be possible. 

 And it is the fundamental way. We are now going to 

 consider some other ways in which numerals are assigned 

 to represent properties ; but it is important to insist at 

 the outset, and to remember throughout; that these 

 other ways are wholly dependent upon the fundamental 

 process, which we have just been discussing, and must 

 be so dependent if the numerals are to represent " real pro- 

 perties " and to tell us something scientifically significant 

 about the bodies to which they are attached. This 

 statement is confirmed by history ; all properties mea- 

 sured in the definitely pre-scientific era were measured 

 (or at least measurable) by the fundamental process ; 

 that is true of weight, length, volume, area and periods 

 of time. The dependent measurement, which we are 

 now about to consider, is a product of definitely and con- 

 sciously scientific investigation, although the actual 

 discovery may, in a few cases, be lost in the mists of the 

 past. 



