NATURE OF THE DIFFERENTIAL INDUCTOMETER. 81 



the time as the plates of a condenser. If only two plates were used, by the proper 

 application of the condenser the same reduction might take place. This expectation 

 is fully justified by an effect already observed and described (1229.). 



1316. In that case the application of the instrument to very extensive research is 

 evident. Comparatively small masses of dielectrics could be examined, as diamonds 

 and crystals. An expectation, that the specific inductive capacity of ciystals will 

 vary in different directions, according as the lines of inductive force (1304.) are 

 parallel to, or in other positions in relation to the axes of the crystals, can be tested : 

 I purpose that these and many other thoughts which arise respecting specific induc- 

 tive action and the polarity of the particles of dielectric matter, shall be put to the 

 proof as soon as I can find time. 



1317. Hoping that this apparatus will form an instrument of considerable use, I 

 beg to propose for it (at the suggestion of a friend) the name of Differential Inducto- 

 meter. 



Royal Institution, 

 March 29th, 1838. 



MDCCCXXXVIII. M 



