402 RECENT PROGRESS IN PHYSICS. 



termed disguised (gebundene) electricity, a designation wbicli Biess 

 shows, in the historical introduction to his memoir, has contributed 

 much towards establishing erroneous views on the nature of induced 

 electricity. 



Lichtenherg first introduced the expression ''bound" electricity into 

 science. He speaks of bound, latent, or dead electricity, in contradis- 

 tinction to free or sensible; he distinguishes from the ordinary elec- 

 trical condition another, in which electricity, although present, is 

 inactive, dead, latent, perfectly analogous to latent heat. — {Erx- 

 leben's Elements of Physics, 3d edition, with additions by Lichtenberg, 

 1Y84, page 499.) 



This has produced very injurious consequences to science, and has 

 given occasion to the strange ideas on the existence of induced or dis- 

 guised electricity, which, obstinately defended as we have already 

 seen, cannot be corrected without much trouble. However, we can 

 now regard the opinion that latent electricity has entirely peculiar 

 properties, as finally refuted. [See note at the commencement of 

 this section.] 



Biot presents the theory of condensers and the Leyden jar some- 

 what in this manner : If to an insulated metallic plate the quantity 

 of electricity 1 be communicated, this will disguise, in a neighboring 

 metalic plate connected with the earth, a quantity of electricity m, 

 which, reacting upon the first plate, will disguise in it the quantity 

 rri^, so that there is remaining only tlie quantity 1 — m^ as free elec- 

 tricity. If E be the greatest quantity of electricity which the insu- 

 lated plate can receive separately, it will continue to receive more in 

 the presence of the condenser plate, until its free electricity amounts 

 to E. Represent by A the whole quantity which the insulated plate 

 is now capable of receiving, and we will have 



A 1 



(1 — m'^) A =r E, hence ^ =. z ^. 



^ ^ E 1 — m~ 



This fraction indicates the ratio of the quantities of electricity which 

 the insulated plate can receive, standing first alone and then in the 

 presence of the condenser ; it expresses, consequently, the condensing 

 power of the apparatus. 



This formula is perfectly admissible in so far as it serves only for 

 illustrating the action of the condenser, but it must be regarded as 

 misused when it is employed for computing the condensing power of 

 the apparatus. Biess has proved that the coefficient of accumulation 

 of the condenser is not a definite quantity, dependent only upon the 

 distance of the plates, but that it varies with the form and magnitude 

 of the condenser plate, v/ith the position of the conducting wire of the 

 plate, with the point in which the collector receives the electricity 

 from the source of excitation, &c. In short, Biess has shown that 

 the coefiicient of acumulation is a quantity which varies in the same 

 instrument from one experiment to another ; that consequently the 

 above formula cannot be used for computing the condensing power of 

 the apparatus. 



I beo; leave to make a few remarks on the manner in which Biess 



