Intelligence and Miscellaneous Articles. 227 



these are the only absolute units represented by standards. There- 

 fore the unit of force might be varied at pleasure ; and the ohms 

 and microfarads at present distributed to the laboratories would no 

 less preserve their value. 



2. The formula which permit passing from the absolute electromag- 

 netic to the absolute electrostatic system, or inversely, are all indepen- 

 dent of the choice of the unit of force. This can be ascertained by 

 glanciDg at the last line of the table given below, which it is easy 

 to calculate. Now these formulae are the only ones of this kind 

 having a theoretic interpretation. 



The units of intensity and electromotive force, on the contrary, 

 depend on the choice of the unit of force. If, for example, it were 

 thought necessary to substitute for the dyne another unit, the ne- 

 cessary operations for measuring these quantities would not be 

 changed, but their numerical result would be enunciated differently : 

 the volt and the weber would have to be replaced by other denomi- 

 nations ; for they are mere denominations, not standards. 



Besides, we can pass from one system of units to any other with 



the help of the following table : — 



c T . Resist- Electromotive noBO ... 



System. Intensity. ance ^ force> Capacity. 



a L EF^ T 2 



Electromagnetic .. i = F~ r= — e= -=- c= — 



4 



Electrostatic .... I = =£- E= _ E=F* C = L 



J- E 



Ratios 



" i T r L 2 e ~ L c = T 2 



Of course the analogous formulae given by authors are equivalent 

 to those of this table ; but they are rather less simple, and they 

 suppose the acceleration to be taken as the measure of the force. 



The remarks just made show that the choice of the unit of force 

 has not the importance which one would at first be tempted to 

 attribute to it, and consequently that it would be easy to change 

 that unit. 



This being admitted, one may ask why the eminent authors of 



M 3 i 



j-j =F ; ft is therefore of the degree /z = LF 2 . The intensity i of the cur- 

 rent is given by Ampere's formula, which is of the degree t^L=F, whence 



LF a . L 



t= = F a . Finally, the electrical resistance r is given by the equation 



n' 2 T = FL, the two members of which represent respectively the electrical 



FL . L 



and the mechanical work j hence r= ^f ; that is to say, r= m; ris there- 

 fore independent of F, which was to be demonstrated. In like manner, 

 the electrical capacity c, derived from the charge eT by referring it ot the 



»T T 



electromotive force e — ri, is of the form — -. . We have therefore 



n r 



