462 Mr. Snow Harris on LigJitning Conductors 



powerful lateral explosions, not only on near bodies, but on 

 bodies at very great distances. This effect, he thinks, 

 in the case of a lightning rod, is a very fearful circqm- 

 stance. 



2. If this deduction be worth anything, it is altogether sub- 

 versive of the use of such rods as a means of protection from 

 lightning. I have thought it right, therefore, to examine 

 carefully the experiments and reasonings, which have led the 

 author to this conclusion ; and since the inquiry bears mate- 

 rially on a question of great public interest, and contains 

 many new phsenomena of electrical action, I hope it may 

 not be considered unworthy a place in your very valuable 

 Journal. 



3. Although Mr. vSturgeon has spoken in a slighting way 

 of me and my experiments, and has laboured hard to invali- 

 date them, I still feel, that any personal consideration is 

 comparatively of minor consequence. I will not therefore 

 trouble your readers on the subject. I merely wish to have 

 it understood, that this is not a reply to that large part of the 

 memoir levelled at myself, but is simply an investigation of 

 tiie author's " Theoretical and Experimental Researches," and 

 of his claims to our confidence as a writer on Electrical Sci- 

 ence. 



4. So long since as the years 1728 and 1729, Mr. Grey ob- 

 served the phaenomena of electrical conduction and insulation. 



{a). Thus a metallic ball, J, fig. 1, (Plate II.) supported on 

 the glass rod g, is said to be insulated, and if electrified, will 

 cause a spark in the opening between the metallic body B 

 and the ball J. 



{h). If we connect the ball J with any distant body c, by 

 means of a metallic wire as in fig. 2, and electrify it as before, 

 the spark will still occur in the opening at the distant body 

 c, the electricity being conducted by the intermediate wire. 



(c). The distance at which this effect may ensue, is very 

 considerable. Mr. Grey succeeded in making it sensible at 

 a distance of 765 feet*. 



(rf). The effect is most sensible when the body B is con- 

 nected with the ground, which places it, by a law of electrical 

 action, in the most favourable state for receiving the spark. 



5. I am desirous to call especial attention to these results, 

 notwithstanding their elementary character, because, as we 

 shall presently see, they are really nothing more or less than 

 the essence of Mr. Sturgeon's ne'w researches, and which lie 

 claims to have considered by all the learned societies of 

 Europe and America. 



* Priestley's History of Electricity, 



