384 On a powerful Fm^d^ the Induction Coil. ^^ 



by the electrometer, exceptin** that as the power of the instru- 

 ment was giTater or leas, so the extreiTie indications of the largest 

 ^sui'fuce con-espondingly increased or diminished. 

 ^^' 24. Jt is well known that the soft static sp^rk between the 

 "ttfrniinah of the coil inflames gunpowder, whilst the explosive 

 ^^dischargcs when the jar is connected only disperse it without 

 inflainmati'jn. Hence it would appear that there is a difference 

 'in the velocity with which the wave or current is transmitted; 

 'lor although the quantity must be very considerable, yet its 

 i'Vclocity appeal's to a certain extent retarded in its passage through 

 ^the induced wire, and that the effect of the jar appears to be 

 ^0 measure out cei'tain quantities, which are transmitted with 

 greater energy and velocity through that poition of the circuit 

 forming the connexion beUveen its own inner and outer coatings, 

 than through those portions by which these coatings are supplied, 

 and hence the difference in the thermal effects of these different 

 vpprtions of the circuit upon metallic wires and gunpowder. 

 •^Y' 25. In order to test the correctness of the foregoing opinion, 

 ^t! small jar of half a square foot was connected in the ordinary 

 tttanner with the coil (par. 7), and a thermo-electrometer placed 

 In the circuit of the jar. A portion of gunpowder was placed 

 V between the points of the discharger. On passing the discharges, 

 ^'the gunpowder was dispersed, but the electrometer indicated the 

 •iisual rise of temperature. On now inserting a wet string as a 

 portion of the circuit of the jar, the discharges lost their noisy 

 character and inflamed the gunpowder, but the thermo-electro- 

 meter remained perfectly unaffected. 

 >^ • 26. Whatever be the character of this secondary wave, or of 

 '''the sources from whence it is derived, it is clear that an amount 

 W^ electrical disturbance is produced far exceeding what we have 

 *<ljiiiy ordinary notions of; and when compared with the results 

 ^cbbtainable from the most powerful apparatus for the develop- 

 j'iHient of frictional electricity, the effects of the latter appear to 

 Udwindle into insignificance. I cannot help feeling, however, 

 that, by having developed a class of phsenomena which are 

 capable of being produced both through the agency of voltaic 

 and frictional electricity, I have established another link of con- 

 nexion between the two agencies, and one which may ultimately 

 1 j«erve to determine the nature of the relationship existing between 

 /(Ahem. In this investigation I am at present engaged, and hope to 

 jihnake further developments the subject of a futui'c communication, 

 -fu. 27. In concluding the present crude paper, 1 may remark 

 jffthat on first witnessing the torrent of discharges from a large 

 ;' Jjeyden jar, I immediately recognized in them an exact corre- 

 «pondence with certain phenomena which I had before observed 

 in expenmjnting with an atmospheric exploring wire during 

 thunder- storms, and of the real character of which 1 had scarcely 



