Upon Caloric as a Cause of Galvanic Currents. 271 



modes of investigation for both, has not only been productive of false 

 general views, but has seriously retarded the developement of the 

 laws which characterise galvanism. Volta's very ingenious attempts 

 to show that metals give rise to electricity by contact, are of this 

 character, inasmuch as they lead to the conclusion that the activity 

 of the pile is dependant upon ordinary electricity ; whereas no such 

 result will be obtained, if we view these electricities in other res- 

 pects. It seems to be no small perversion, to use the gold leaf elec- 

 trometer for the analysis of a battery, composed of two metallic plates, 

 when it is well knovs^n that this instrument, even with the assistance 

 of doublers, is incapable of indicating the galvanic currents of a bat- 

 tery composed of several hundred plates. Yet such was the instru- 

 ment in common use, until Oersted pointed out the value of the 

 magnetic needle. Even now, that we possess this highly appropri- 

 ate and delicate indicator, we incline strongly to confound ordinary 

 electricity with galvanism, notwithstanding that the former, in its most 

 concentrated condition, has no marked influence upon the galvanom- 

 eter. Whatever may be our inclination to generalize, these simple 

 instruments can alone sustain the opposition, since each one is ex- 

 cessively delicate towards its appropriate fluid, and absolutely good 

 for nothing, for the other. Very many circumstances might be men- 

 tioned, in order to prove that common and voltaic electricities should 

 be considered, in our investigations, as essentially different ; and the 

 late discoveries with the magnet seem to point strongly to some ulte- 

 rior and elementary condition, which must certainly, ere long, give 

 us more correct views, and, most probably, mark the distinction, here 

 noticed, more closely. 



To this limitation I shall confine myself, at all events, and wherever 

 the term electricity may appear in my remarks, it must be under- 

 stood to refer to galvanism, unless the contrary be stated. The ex- 

 periments were made with a galvanometer consisting of about one 

 hundred coils, and constructed like the multiplier. 



The simplest view of the relation, existing between caloric and 

 galvanism, is presented by thermo-electric combinations : I shall^ 

 therefore, proceed first, to this portion of the subject and reserve my 

 remarks upon hydro-electricity, or that produced by metals and chem- 

 ical solutions for a subsequent communication. 



Thermo-electricity. — We are indebted chiefly, to the investigations 

 of Gumming, Becquerel and Nobili, for most of the particulars 

 which relate to the electric powers of combined metals, when exposed 

 to heat, and it appears clear from their results, that the currents 



