134 WHAT IS SCIENCE? 



is essential to the discovery of laws that it is of such vital 

 importance to science. 



One final remark should be made before we pass on. 

 In this chapter there has been much insistence on the 

 distinction between fundamental measurement (such as 

 is applicable to weight) and derived measurement (such 

 as is applicable to density). And the distinction is 

 supremely important, because it is the first kind of 

 measurement which alone makes the second possible. 

 But the reader who, when he studies some science in detail, 

 tries, as he should, to discover which of the two processes 

 is involved in the measurement of the various properties 

 characteristic of that science, may occasionally find 

 difficulty in answering the question. It should be pointed 

 out, therefore, that it is quite possible for a property to 

 be measurable by both processes. For all properties 

 measurable by the fundamental process must have a 

 definite order; for the physical property, number, to 

 which they are so similar, has an order the order of 

 " more " or " less." This order of number is reflected 

 in the order of the numerals used to represent number. 

 But if it is to be measurable by the derived process, it 

 must also be such that it is also a " constant " in a numeri- 

 cal law a term that is just going to be explained in the 

 next chapter. There is nothing in the nature of funda- 

 mental measurement to show that a property to which it 

 is applicable may not fulfil this condition also ; and some- 

 times the condition is fulfilled, and then the property is 

 measurable either by the fundamental or the derived 

 process. However, it must be remembered that the pro- 

 perties involved in the numerical law must be such that 

 they are fundamentally measurable ; for otherwise the 

 law could not be established. The neglect of this condi- 

 tion is apt to lead to confusion ; but with this bare hint 

 the matter must be left. 



