382 



RECENT PROGRESS IN PHYSICS. 



SECTION SECOND. 



INDUCTION OF ELECTRICITY. 



[This title is translated by words having a very different sense in English from those used 

 in the German. The original is " Verlhdlung und Bindung der Electricitat " — literally, Dis- 

 tribution and Binding of Electricity. The verb vertheilen, which we translate by "induce," ia 

 80 strictly parallel in all its derivatives with the corresponding English word that, although 

 the original meanings are not the same, we need make no further remark upon this point. 



But, although we may translate" bound" into "disguised," we cannot with equal propriety 

 speak of an electrified conductor as "disguising" electricity in a body brought near to it; the 

 German would say "binding." In some English translations of German works on electricity, 

 the words "combine," "combined," and "combination," are used; these are not only incor- 

 rect, but lead to an idea diametrically opposed to the true one. In general for " bind" we 

 have used simply "induce," sometimes the more precise periphrasis "render latent." In 

 general "latent" and "disguised" are used synonymously. 



A good English word nearly identical in meaning with the German one, and capable of being 

 used in all the corresponding modifications, would be "engage" — thus we might speak of a 

 conductor "engaging" electricity, of "engaged" electricity, and on the contrary of " disen- 

 gaged" or free electricity. 



But as there is no authority for the use of this term we have not ventured to introduce it. 



These remarks are rendered necessary by the fact that in many places the force of the 

 original is lost in the circumlocution required in the English. 



The introduction to § 26, and the first foot note after it, should be read with reference to 

 these difl[iculties in the translation. 



In strictness the term "latent electricity" is improper as implying an analogy with latent 

 heat. Even "disguised electricity" is not really correct, as it is one of the main objects of 

 this section, to show that electricity in this condition loses none of its properties. But we 

 may here refer to the remark of our author, that terms in themselves not strictly accurate, 

 may be safely used after correct ideas have beeu connected with them.] 



§ 17. Introduction. — The mode in which Blot has exhihited the in- 

 duction of electricity on an insulated body, to which an electrified 

 body is approached, should be sufficient to remove every doubt as to 

 the nature of induction ; yet a controversy on this subject has arisen, 

 from the objection of Pfoff. 



An account of this controversy is given in the second volume of 

 Dove's Repertorium, page 29. 



Fig. 20. 



Let a body m, (fig. 20,) charged 

 with positive electricity, be brought 

 near an insulated conductor c, then 

 will c, as it is well known, be elec- 

 trified by induction ; at the end near- 

 est m, is to be found the attracted 

 — E, and at the opposite end the re- 

 pelled -f- E, as shown by the proof plane. 



If the insulated conductor be touched, the repelled electricity will 

 be conducted off, while the electricity attracted by ni remains disguised 

 or latent at c. 



Pfoff contended that this disguised electricity could not act in all 

 directions, while Biot showed its free activity by suspending at the two 

 ends of the conductor electrical pendulums, which diverged ; those at 



