108 



PROTECTION FROM LIGHTNING. 



one ball placed very close to one part of the wire, and the other ball very close 

 to another part, a spark will appear at each ball. In this case, it is evident 

 that the metal of the discharging-rod was of no ultimate service in furnishing 

 a side-path as a thoroughfare to the charge, but merely relieved the portion of 

 the wire intervening between the balls. The same effects occur during the 

 discharge of a Leyden battery, especially when it is insulated. But not only 

 is it possible to obtain a spark from the wire itself, but even from any metallic 

 system with which the wire is connected. We have ourselves obtained it from 

 gas-burners in all parts of a very large building, when the wire was connected 

 with the gas-pipes in one part. 



This spark is much more readily obtained from the prime conductor than 

 from the Leyden discharger, obviously on account of the low intensity of the 

 latter, for it is an effect of intensity alone which enables electricity to pass at 

 all through the air. Voltaic electricity, of which we shall hereafter speak, is 

 abundant in quantity, but of such low tension as not to pass at all before contact, 

 unless from a very extensive series of the pile. 



Now the law which regulates all discharges is, that they pursue the line or 

 lines of least resistance. When, therefore, the sum of two paths, including the 

 interval or intervals of air, involves less resistance than does the one original 

 path, the division occurs ; when it involves greater resistance, it does not oc- 

 cur ; and this readily explains the greater facility for lateral discharge display- 

 ed by the electricity from the conductor, as contrasted with the Leyden flash. 

 At the very outset the former will overcome the resistance of many inches of 

 air, while the latter is insulated by less than one inch, and hence* the former 

 has, throughout its brief existence, a power greatly exalted over that of the 

 other. And this path, or paths, is not a mere matter of choice, determined on 

 by the charge in its progress onward ; it is a course entirely marked out by the 

 action of induction, antecedent to the original discharge. Indeed, it is the mere 

 fact of the inductive action being able to find a path offering a resistance which 

 the charge can overcome that first causes the discharge to take place. There 

 are other instructive facts connected with the lateral discharge, for which we 

 have not space here, and to which the reader must refer.* 



* Vide Naut. Mag., Jan., 1840 ; Report of Committee of House of Commons on Lightning ; Ann. 

 Elect, 1840; Proceed. Elect. Soc., 1842; Harris, on Thunder-Storms, 1843. 



