558 



TABLE OF DIMENSIONS. 



convenience of this there can be no question, but the question of 

 units seems now to be beyond the control of theoretical writers*. 



A system of units has been proposed by Dr Johnstone Stoneyf, 

 who advocates the choice of units so as to make the velocity v the 

 unit of velocity. This would make the numerical measure of all 

 quantities the same in both electrostatic and electromagnetic 

 units, which would be convenient, but inasmuch as the velocity v 

 is not yet accurately known, the proposal is hardly practical. 



A table of dimensions of the principal electric and magnetic 

 quantities is annexed. 



TABLE OF DIMENSIONS. 



Quantities. 



Fundamental Units. 



Length 



Mass 



Time 



Derived Units. 



Area 



Volume 



Angle 



Solid Angle 



Velocity 



Angular Velocity 



Acceleration 



Momentum 



Force 



Pressure 



Energy 



Activity or Power 



Energy-Density 



Energy-Current-Density 



Dimensions. 



L 

 M 

 T 



L? 

 L s 



T~ l 

 LT~* 



MLT~ l 

 MLT~* 

 ML~ l T 



ML* T~ s 

 ML- 1 T 



MT~ 3 



* Heaviside. "The position of 4?r in Electromagnetic Units. 1 

 28, 1892, p. 292 ; Papers, Vol. n. p. 575. 

 f B. A. Eeport, 1891. 



Nature, July 



