ELECTRICAL UNITS OF MEASUREMENT. 95 



of absolute reckoning of force by Gauss cannot 

 be too much commended, as a great and important 

 practical improvement in the fundamental science 

 of engineering and physics, the science of dyna- 

 mics. It consists simply in defining the unit of 

 force as that force which, acting on a unit of mass 

 for a unit of time, generates a velocity equal to the 

 unit of velocity. It leaves the units of mass, 

 length, and time to be assumed arbitrarily ; the 

 gramme, the centimetre, . and the mean solar 

 second, for example, as in the now generally 

 adopted " C. G. S." system. 



But the universal-gravitation system of the 

 dynamical astronomer defines the unit of mass 

 in terms of the unit of length and the unit of force. 

 I need not repeat the definition. Thus we have 

 the interlocking of two definitions : the unit of 

 force defined in terms of the units of mass, length, 

 and time ; the unit of mass defined in terms of the 

 unit of force and the unit of length. It might 

 seem as if we were proceeding in a vicious circle ; 

 but the circle is not vicious, the two definitions 

 are logically and clearly inter-dependent. We 



