118 ANNUAL OF SCIENTIFIC DISCOVERY. 



was for a time thought to denote a new property of the electric current. 

 But Rijkc had shown in a paper, the interest of which is by no means less- 

 oned bv the modesty with which it is written, that the effect observed by 

 1'age is due to the sudden extinction of the primary spark by the magnet; 

 which suddenness concentrates the entire force of the extra current into a 

 moment of time. Speaking figuratively, it was the concentration of what, 

 under ordinary circumstances, is a mere push, into a sudden kick of projec- 

 tile energy. 



7. The contact-breaker of an induction coil was removed, and a current 

 from five cells was sent through the primary wire. The terminals of the 

 secondary wire being brought very close to each other, when the primary 

 was broken by the hand, a minute spark passed between the terminals of the 

 secondary. When the disruption of the primary was effected between the 

 poles of an excited electro-magnet, the small spark was greatly augmented 

 in brilliancy. The terminals were next drawn nearly an inch apart. When 

 the primary was broken between the excited magnetic poles, the spark from, 

 the secondary jumped across this interval, whereas it was incompetent to 

 cross one-fourth of the space when the magnet was not excited. This result 

 was also obtained by Rijkc; who rightly showed, that in this case also the 

 augmented energy of the secondary current was due to the augmented speed 

 of extinction of the primary spark between the excited poles. This.experi- 

 mcnt illustrated in a most forcible manner the important influence which the 

 mode of breaking contact may have upon the efficacy of an induction coil. 

 The splendid effects obtained from the discharge of Ruhmkorff's coil through 

 exhausted tubes were next referred to. The presence of the coil had compli- 

 cated the theoretic views of philosophers, with regard to the origin of those 

 effects ; the intermittent action of the contact-breaker, the primary and second- 

 ary currents, and their mutual reactions, producing tertiary and other currents 

 of a higher order, had been more or less invoked by theorists, to account for the 

 effects observed. Mr. Gassiot was the first to urge, with a water battery of 

 three thousand five hundred cells, a voltaic spark across a space of air, before 

 bringing the electrodes into contact; with the self-same battery he had ob- 

 tained discharges through exhausted tubes, which exhibited all the pheno- 

 mena hitherto observed with the induction coil. He thus swept away a host 

 of unnecessary complications which had entered into the speculations of 

 theorists upon this subject. 



8. On the present occasion, through the kindness of Mr. Gassiot, the 

 speaker was enabled to illustrate the subject by means of a battery of four 

 hundred of Grove's cells. The tension at the ends of the battery was first 

 shown by an ordinary gold-leaf electroscope ; one end of the battery being 

 insulated, a wire from the other end was connected with the electroscope; 

 the leaves diverged ; on now connecting the other end of the battery with 

 the earth, the tension of the end connected with the electrometer rose, ac- 

 cording to a well-known law, and the divergence was greatly augmented. 



9. A large receiver, in which a vacuum had been obtained by filling it with 

 carbonic acid gas, exhausting it, and permitting the residue to be absorbed 

 by caustic potash, was placed equatorially between the poles of the large 

 electro-magnet. The jar was about six inches wide, and the distance be- 

 tween its electrodes was ten inches. The negative electrode consisted of a 

 copper disk, four inches in diameter; the positive one was a brass wire. An 

 accident had recently occurred to this jar. Mr. Faraday, Mr. Gassiot, and 

 the speaker had been observing the discharge of the nitric acid battery 



