ELECTRICAL UNITS OF 

 MEASUREMENT. 



[A Lecture delivered at the Institution of Civil Engineers 

 011 May 3, 1883 ; being one of a series of Six Lectures 

 on "The Practical Applications of Electricity."^ 



IN physical science a first essential step in the 

 direction of learning any subject is to find prin- 

 ciples of numerical reckoning and methods for 

 practicably measuring some quality connected with 

 it. I often say that when you can measure what 

 you are speaking about, and express it in numbers, 

 you know something about it ; but when you can- 

 not measure it, when you cannot express it in 

 numbers, your knowledge is of a meagre and un- 

 satisfactory kind : it may be the beginning of know- 

 ledge, but you have scarcely, in your thoughts, 

 advanced to the stage of science, whatever the 



