and on certain Principles in Electrical Science. 465 



*' The effect," he says, '' is much increased by connecting the 

 body B with the ground, and diminished to a certain extent 

 by connecting the outside of the jar with the ground." I 

 have produced the spark, he says, between c c, and the 

 body B when placed at 50 feet from the direct discharge. 



" By this kind of lateral discharge," he observes, " a dense 

 spark may be produced when the bodies B and c c, fig. 3, are 

 half an inch apart. Though the jar be only of the capacity of 

 a quart, chemical decompositions may be effected by it." 



10. Mr. Sturgeon does not state precisely how these ex- 

 periments were conducted, but the nature of the manipula- 

 tions would have a material effect on the result. If for ex- 

 ample a small jar of a quart capacity were charging from a 

 very powerful machine, and the discharge produced at the 

 time of charging, either by a spontaneous explosion between 

 the balls, ?nc, fig. 3, or by an insulated discharger, then, as 

 is evident, not only would the outer coating and its append- 

 ages become charged with the residuary electricity proper to 

 the jar, but also by electricity from the prime conductor, 

 which would assuredly pass over at the instant of the dis- 

 charge. In Mr. Sturgeon's account of his experiments this 

 fallacious method would appear to have been resorted to. 

 He says, " a spark is felt at every discharge through the cir- 

 cuit represented in the figure," that is ?w c c, fig. 3. Now the 

 continued discharges implied in this statement, could only be 

 produced by continuing to work the machine in connexion 

 with the jar. This circumstance alone would be sufficient to 

 falsify the whole. 



11. The following experiments are not unimportant as 

 bearing on the present question. 



(k). Let ajar, J, fig. 3, be charged positively, removed from 

 the machine, and insulated. — Under this condition discharge it. 

 When discharged, let the electrical state of the knob m, dis- 

 charging conductor c c, the outer coating J, or any distant 

 body cc, fig. 4, connected with it, be examined ; they will all 

 be found in the same electrical slate, which state will be pre- 

 cisely that, exhibited by the outer coating and knob, whilst 

 charging, and the small residuary spark will be jilus. 



(/). Charge the jar as before; but before discharging it, 

 withdraw the free electricity from the knob. The electrical 

 state of the coating and appendnges will be now changed, 

 and the small residuary spark will be minus. 



(;«). Immediately (iftcr the discharge, apply a metallic body 

 B, figs. 3 and 4, either to the coating J, or any body con- 

 nected with it. A residuary spark will be thrown off. 



{7i). Place a metallic body B near the discharger, or outer 

 Phil. Mag. S. 3. Vol. 15. No. 98. Dec. 1839. 2 H 



