282 On Lightning Conductors to Poivder Magazines, [No. 99. 



comparatively well understood ; that it is only between objects 

 susceptible of rapid changes in their electric relations that the 

 explosion passes, but that the explosion may exceed in quan- 

 tity and in intensity the capabilities of the dischargers we usu- 

 ally adopt. 



15. Another reason for objecting to the employment of 

 conductors in the immediate contiguity of powder magazines 

 is, the danger of their inducing what is called the " lateral dis- 

 charge," of the nature of which I will venture to offer a few ex- 

 planatory remarks. 



16. Suppose a violent discharge to take place along the 

 conductor a to the ground; during the passage of the electri- 

 city an opposite electric state is induced in contiguous ob- 

 jects, and a spark may pass in the interval between a and b 9 

 and all the articles contained within having their electric state 

 transitorily disturbed, will give sparks at the same moment ; — 

 if animate, will experience shocks or other effects in proportion 

 to the violence of the primaiy discharge. Thus the inmates 

 of Dr. Goodeve's house suffered a shock like the discharge of 

 the Leyden bottle, at the instant the accident took place, des- 

 cribed at paragraph 8. 



17. Were any peculiarly in- 

 flammable matter existing in the 

 interval a, b, or in the interstices 

 c, d y the passage of a spark would 

 cause its inflammation, especially 

 if rain were falling at the same 



time. The explosion of gunpowder by small electric sparks is 

 indeed never certain, but when water or moist substances forms 

 part of the electric circuit. 



18. I will not enter on any detailed consideration of the 

 dangers connected with what is called the cc return discharge/* 

 in which the electricity is believed to emanate from terrestrial 

 objects, and proceed to the atmosphere. Precise facts are want- 

 ing to enable us to form exact opinions on this subject. 



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