120 WHAT IS SCIENCE? 



most important part, of experimental science. Whenever 

 a new branch of physics is opened up (for, as has been 

 said, physics is the science that deals with such processes of 

 measurement), the first step is always to find some process 

 for measuring the new properties that are investigated ; 

 and it is not until this problem has been solved, 

 that any great progress can be made along the branch. 

 Its solution demands the discovery of new laws. We 

 can actually trace the development of new measurable 

 properties in this way in the history of science. Before 

 the dawn of definite history, laws had been discovered 

 which made measurable some of the properties employed 

 by modern science. History practically begins with 

 the Greeks, but before their time the properties, weight, 

 length, volume, and area had been found to be measur- 

 able ; the establishment of the necessary laws had prob- 

 ably occurred in the great period of Babylonian and 

 and Egyptian civilization. The Greeks, largely in the 

 person of Archimedes, found how to measure force by 

 establishing the laws of the lever, and other mechanical 

 systems. Again from the earliest era, there have been 

 rough methods of measuring periods of time, 1 but a true 

 method, really obeying the three rules, was not discovered 

 till the seventeenth century ; it arose out of Galileo's 

 laws of the pendulum. Modern science has added greatly 

 to the list of measurable properties ; the science of elec- 

 tricity is based on the discoveiy, by Cavendish and 

 Coulomb, of the law necessary to measure an electric 

 charge ; on the laws, discovered by (Ersted and Ampere, 

 necessary to measure an electric current ; and on the 

 laws, discovered by Ohm and Kirchhoff, necessary to 



1 By a period of time I mean the thing that is measured when we 

 say that it took us 3 hours to do so-and-so. This is a different 

 " time " from that which is measured when we say it is 3 o'clock. 

 The difference is rather abstruse and cannot be discussed here ; but 

 it may be mentioned that the " measurement " involved in "3 

 o'clock " is more like that discussed later in the chapter. 



