180 Mr. Snow Harris 07i Lightning Conductors^ 



between these 



ri' 



a 



M 



with the least spark of electricity, was placed 

 interruptions. On its surface M was placed 

 a continuous conductor e M.f, and the in- 

 terior and exterior lines of metal connected 

 with common points of junction at a and d. 

 To make the experiment more complete, 

 bands of metallic leaf, &c. were made here 

 and there to surround the mast, together 

 with other metallic bodies, which could en- 

 ter into the mast itself and touch the me- 

 tallic line within, as at 1, 2, 3. 



An intense electrical accumulation from 

 four jars of five square feet each, highly 

 charged, was now allowed to fall upon a ball 

 at «, with a view of discovering (since the elec- 

 tric matter had a choice of two lines) whether 

 it would pass upon the metal within in 

 preference to that without, or upon both, or 

 whether it could in passing down the exterior 

 conductor cause a lateral discharge to enter 

 the mast, or aflfect the interior by any other 

 lateral result. 



Now the extreme facility with which per- 

 cussion powder becomes inflamed by the 

 most minute spark, rendered it a very severe 

 test of the presence of passing electricity, so 

 that if the least action had taken place upon 

 the metallic bodies adjacent to the conductor, 

 it would have been immediately shown by 

 an explosion within the substance of the mo- 

 del. Almost every one must 1 think perceive 

 that this was a fair experiment, and as good 

 a one as could have been resorted to under 

 the circumstances of the case. Even Mr. 

 Sturgeon himself must allow that it com- 

 pletely meets the very points he has insisted 

 on, and which he thinks I had so much over- 

 looked. Thus in sect. 202 of liis memoir, ** 

 mistaking the residual electricity of a discharged surface for 

 what he calls a lateral discharge produced by the passing 

 shock, he says, " this kind of lateral discharge will always 

 take place when the vicinal bodies are sufficiently capacious, 

 and near to the principal conductor xohich carries tJie jwimitive 

 discharge, or to any of its metallic appendages •" and in sects. 

 198 and 199, he says he can produce lateral discharges 

 half an inch long, though the jar be of the capacity of a quart 



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