46i Mr. Snow Harris on Lightning Conductors 



By bringing a metallic ball, B, fig. 3 and 4, therefore in a 

 free state, either very near the discharging rod c c, fig. 3, the 

 outer coating J, or any body, c, fig. 4, in connexion with it, 

 previously to making the discharge, we seize as it were some 

 of the residuary electricity before it has time to pass off, and 

 hence it becomes evident in this particular direction. The 

 effect, however, will be necessarily greatest when the jar and 

 its appendages are quite insulated. After this spark has taken 

 place, the jar will be found again slightly charged, with what 

 has been called a residuary charge, so that the phasno- 

 menon itself is actually the same as that already observed in 

 charging the jar originally [e). 



7. Now these simple experiments i^g)^ {li\ {i), are just the 

 experiments described by Mr. Sturgeon, in which he imagines 

 that the small spark above described, is produced by a lateral 

 action of the rod carrying off the discharge. He seems to 

 consider it as a novel and important fact, and calls upon the 

 " principal scientific bodies in Europe and America," and 

 " the ablest electricians the world can produce," in order 

 that it may be fully sifted and explained. He takes great 

 credit for having placed this subject before them in a " j^ro- 

 per light," and cannot account for the circumstance of my 

 having overlooked it*. 



8. But since it is clear that this supposed lateral explosion 

 really resolves itself into one or two simple facts (a) (b), 

 known to electricians for more than a century since, " the 

 ablest electricians the world can produce," may perhaps be 

 disposed to think such an occupation of their time unne- 

 cessary, and the several " Learned Societies in Europe and 

 America " may consider it would have been quite as well for 

 Mr. Sturgeon's credit, as a lectui'er on natural philosophy, if 

 he had not troubled them on the occasion. 



9. The following is Mr. Sturgeon's version of these ex- 

 periments : 



This kind of lateral discharge, " consists in the displace- 

 ment of the electrical fluid of bodies vicinal to a continuous 

 conductor carrying the primitive discharge." 



Exp. — If a Leyden jar, J, fig. 3, be discharged through a 

 rod c c, a spark will appear at the opening o, between the 

 metallic body B placed near the rod. 



Exp. — If instead of discharging the jar through the rod 

 cc, fig. 4, we discharge it by a common discharging rod f, 

 still the spark will appear at o as before. 



* " I mean to submit the substance of my Memoir to the consideration 

 of the principal scientific bodies in Europe and America, in order that 

 the subject may be fully sifted and explained by the ablest electricians the 

 world can produce." — Ann. of Elect., p. 191. 



