1883.] Mr. C. Vernon Boys on Meters for Power and Electricity. 235 



WEEKLY EVENING MEETING, 



Friday, March 2, 1883. 



William Bowman, Esq. LL.D. F.R.S. Honorary Secretary and 



Vice-President, in the Chair. 



C. Vernon Boys, Esq. 



Meters for Poioer and Electricity. 



The subject of this evening's discourse : — " Meters for Power and 

 Electricity," is unfortunately, from a lecturer's point of view, one of 

 extreme difficulty ; for it is impossible to fully describe any single 

 instrument of the class without diving into technical and mathematical 

 niceties which this audience might well consider more scientific than 

 entertaining. If then, in my endeavour to explain these instruments 

 and the purposes which they are intended to fulfil, in language as 

 simple and as untechnical as possible, I am not as successful as you 

 have a right to expect, I must ask you to lay some of the blame on 

 my subject and not all on myself. 



I shall at once explain what I mean by the term " meter," and I 

 shall take the flow of water in a trough as an illustration of my 

 meaning. If we hang in a trough a weighted board, then, when the 

 water flows past it, the board will be pushed back : when the current 

 of water is strong, the board will be pushed back a long way : when 

 the current is less it will not be pushed so far: when the water 

 runs the other way the board will be pushed the other way. So by 

 observing the position of the board, we can tell how strong the current 

 of water is at any time. Now suppose we wish to know, not how 

 strong the current of water is at this time or at that, but how much 

 water altogether has passed through the trough during any time, as 

 for instance, one hour. Then, if we have no better instrument than 

 the weighted board, it will be necessary to observe its position con- 

 tinuously, to keep an exact record of the corresponding rates at which 

 the water is passing, every minute, or better every second, and to add 

 up all the values obtained. This would, of course, be a very trouble- 

 some process. There is another kind of instrument which may be used 

 to measure the flow of the water: — a paddle-wheel or screw. When 

 the water is flowing rapidly the wheel will turn rapidly, when slowly, 

 the wheel will turn slowly, and when the water flows the other way, 

 the wheel will turn the other way, so that, if we observe how fast the 

 wheel is turning we can tell how fast the water is flowing. If now 

 we wish to know how much water altogether has passed throuf^h the 

 trough, the number of turns of the wheel, which may be shown by 

 a counter, will at once tell us. There are therefore, in the case of 

 water, two kinds of instruments, one which measures at a time, and 



