Mr. W. Sturgeon on the Theory of Magnetic Electricity. 203 



duced too rapidly to be separately considered, it is the aggre- 

 gate of the multitudinous electro-pulsations constituting the 

 general discharge, that is to be understood by the term electro- 

 momentum when a voltaic battery is the instrument employed 

 for generating the electric currents. 



Thermo-electric currents are also, in some cases, of a pul- 

 satory character ; for, as several of the metals are constituted 

 of crystals, and those crystals of distinct elementary metallic 

 films (see my paper on the Thermo-magnetism of simple 

 metals, Phil. Mag. and Annals, vol. x.), the heat, which 

 in this case is the impelling agent, must necessarily arrive at 

 a certain degree of concentration, or of intensity, if you please, 

 in one film, or distinct metallic element, before it can possibly 

 take possession of the next. Consequently, however small and 

 inappreciable may be the interruption in each stage of its 

 progress, each interruption must necessarily produce a virtual 

 pause; the very existence of which in the advances of heat 

 from film to film will constitute a pulsatory progression. 



In the Marechausian* (colonne pendule), or dry electrical co- 

 lumn, the electro-pulsations are, in consequence of the very 

 great number of interrupting papers, less frequent than in 

 either the process of Volta, or in that of Seebeck. Notwith- 

 standing which, the instrument produces slow pulsatory cur- 

 rents. 



The favourite term intensity, so frequently pressed into the 

 service of some writers, appears to have no definite meaning 

 in the vague manner which it is generally employed. It occurs, 

 sine discriminatione, in electro- statics and electro-dynamics 

 as if no real difference existed in the two distinct conditions of 

 the electric matter; and as it is very far from being expressive 

 of either of them, it can never be intelligibly employed in that 

 double capacity. 



When first introduced as a technical term in electricity, it 

 appears that intensity was intended to express degree of an 

 electro-statical charge ; and it has never yet been employed to 

 denote distinctly an electric force constituted of quantity and 

 velocity. Intensity, therefore, cannot be considered as syno- 

 nymous with momentum, which admits not of being warped 

 into electro-statics, nor of being dispensed with in electro- 

 dynamics. 



The term induction is in precisely the same predicament as 

 that of intensity, and may very justly be considered as a fel- 

 low slave, variously, and often unintelligibly, employed. 



Position 3. — When the metallic body moves in any given 



* M. Marechaux appears to have constructed the first dry electric co- 

 lumn— Ann. de Chim. for January 1806. 



' ° D 2 



