378 MEMORIAL O:F JOSEPH HENRY. 



arc) will fail to give us strong currents, but we may increase the 

 current by joining the same cells in series. - - - Cells joined 

 in series are sometimes described as joined for 'intensity'; and cells 

 joined in multiple arc, as joined for 'quantity.' These terms are 

 remnants of an erroneous theory." * 



Again, in speaking of galvanometers of long and fine coils, as 

 distinguished from those of short and thick wire coils, he says : " In 

 some writings these two classes of instruments are spoken of as 

 adapted to two different classes of 'currents' instead of to two 

 different classes of circuits. The instrument with numerous turns 

 of fine wire is said to indicate 'intensity' currents, the other class 

 to indicate 'quantity' currents. These two old names survive, 

 although the fallacious theory which assumed that there were two 

 kinds of currents is extinct: the term 'intensity galvanometer' is 

 used to signify an instrument with thousands of turns of thin wire 

 in its coil, and 'quantity galvanometer' an instrument with few 

 turns of thick wire. I shall name the two varieties 'long coil' 

 and 'short coil' galvanometers." f 



Admirable as the mathematical theory of galvanic circuits has 

 proved itself in its fullness and precision, it does not supply us with 

 any satisfactory physical conception of the palpable dynamic differ- 

 ence in the resultant galvanic currents. The old terms, whether 

 accurate or not, are still convenient designations of the acknowl- 

 edged differences when reference is had to effects rather than to 

 arrangements. J 



No one has more clearly pointed out the almost constant an- 

 tithesis between the actions of "static" and "dynamic" electricity, 

 than Peltier himself. "Static electricity is duplex; each of its 

 forms is collected, controlled, and maintained separately; being 

 manifested only in the state of isolation and separation : these forms 

 are only preserved thus separate by non-conducting substances, and 

 their action endures as long as their insulation. Dynamic electricity 

 is not double; it cannot be separately either collected, controlled, 

 or maintained ; being manifested only at the instant of its trans- 

 mission through conductors insulated or not : for continuous effect 

 it is necessary that the producing cause be continuous. The former 

 collects only at the surface, being equally or unequally distributed 

 thereon according to the form of the surface. The latter is propa- 



* Electricity and Magnetism. By Fleeming Jenkin. 16mo. London and New 

 York, 1873, chap. iv. sect. 7, p. 88. 



t Same work, chap. xiii. sect. 3, p. 190. 



t Peltier from experiments (the results of which he has detailed) controverted 

 the universality of the law of Ohm and Gauss, that galvanic resistance is directly 

 proportioned to the length of the conducting wire, and inversely proportional to 

 the area of its cross-section. (Oomptes Rendus, Oct. 12, 1835, vol. i. pp. 203, 204.) 



