Metallic Bodies by Voltaic Electricity. 221 



heated ; when less, then the inferior conductor is the most 

 heated. 



22. These experiments seem calculated to establish many 

 important points connected with voltaic action, nevertheless it 

 is always essential to remember, that, with our present imperfect 

 apprehension of the causes of electricity and heat, an exact 

 knowledge of every observed effect cannot be fairly expected ; 

 the results of these and similar inquiries, therefore, must be con- 

 sidered merely as useful approximations toward a higher degree of 

 theoretical perfection. The instrument resorted to in prosecuting 

 the foregoing researches, although not entirely without the limit 

 of objection, is, nevertheless, convenient, and useful in practice, 

 and sufficiently perfect for the purposes to which it is intended 

 to be applied. In cases where it is thought desirable, mercury, 

 as already observed (2), may be used for indicating the degrees 

 of force instead of the coloured fluid : in this case, however, the 

 tube for regulating the divisions on the scale should be much 

 finer. 



PLYMOUTH, May 5. 1831. 



VOL. XII. PART I. F f 



