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much versed in voltaic science, to describe the instruments 

 and processes by which voltaic currents have hitherto been 

 estimated. 



I make use of the term " current" to express the effect 

 which is communicated by conductors, through which elec- 

 tricity is supposed to pass. There is no science in which 

 greater difficulty has been found in using appropriate and 

 unexceptionable names and terms than in electricity. The 

 terms which have been used in most sciences have been such 

 as expressed, or were supposed to be in accordance with, the 

 then theories and ideas. Such theories have since, in many 

 cases, been found incorrect ; and the terms have consequently 

 proved not only inapplicable, but detrimental, from their 

 conveying false ideas, which, when once acquired, are with 

 difficulty eradicated or corrected. The best terms in all 

 sciences would be those which should not express any definite 

 meaning at all. But it would be most difficult to fix such 

 terms in the mind. It is, therefore, best to use expressions 

 which have a general meaning, but which do not convey ideas 

 appertaining to any particular theory. The term voltaic 

 current has been generally adopted, and is one of the most 

 unexceptionable ; but even in using this term I must beg to 

 be understood not to mean that any fluid, thing, or matter 

 passes, but merely that a cause or force producing an effect 

 is transmitted; and that I do not express any opinion that 

 we have yet any real knowledge of the nature of electricity, 

 though I may on some future occasion have the pleasure of 

 laying before you some speculations or proposed theory on 

 the subject. 



The following methods have been used for estimating the 

 force of voltaic currents:. — 



By observing the length of platina wire, of a given thick- 

 ness, heated to redness by the current. In this method it is 

 difficult to observe the exact length and degree of ignition. 



