346 



Observer — Ao. XVIII. 



Vol. III. 



For the Farmers' Cabinet. 



Observer— Wo. XVIII. 



ELECTRICAL CONDUCTORS. 



On lookino- over a late number of tlie Cab- 

 inet, page 261, I observed an inquiry in rela- 

 tion to electrical conductor.s. The writer ap- 

 pears to wish information to what distance a 

 rod will extend its protecting influence, or in 

 other words, whetlier a large building should 

 be furni.-ihed with more than one conductor. 

 I have already stated (p. 7-3) tiiat no such dis- 

 tance can be assigned, because it continually 

 varies from nothino-, up to an indeterminate 

 extent, as the intensity of tlie electrical charge 

 and other circumstances vary. Perhaps an 

 illustration of principles may be satisfactory 

 to some of my readers. 



When a body is charged with electricity it 

 is found to acquire what is called an electri- 

 cal atmosphere — that is, the air for some dis- 

 tance around it presents electrical phenomena. 

 The distance to which this atmosphere ex- 

 tends, and the intensity of the phenomena 

 which it presents, increase with the intensity 

 of the charge. 



This atmosphere extends to many times the 

 striking distance of the charged body, (fig. 39.) 



/ 

 111'// 





wtMw 



Both the existence and the extent of the 

 electrical atmosphere may be determined by 

 bringing the back of the hand within its in- 

 fluence, when a peculiar sensation will be felt 

 long before it approaches near enough to re- 

 ceive a spark. 



I will offer the following in explanation: — 

 The particles of the electrical fluid have a 

 strong mutual repulsion for each other, caus- 

 ing them to separate witli a force which in- 

 creases with the diminution of their distances. 

 But these particles powerfully attract, and are 

 attracted hy other bodies, so as to collect upon, 



and from an atmosphere around them as in the 

 figure. Their repulsive force is counteracted 

 in part by the attraction of the body, and in 

 part resisted by the air which surrounds them, 

 and in a dry state is a non-conductor of elec- 

 tricity. Hence, as the electricity accumu- 

 lates upon any body, its expan.<ive force in- 

 creases, and the electrical atmosphere is ex- 

 tended to a greater distance, where they find 

 an equilibrium between that force which 

 causes them to diverge, and the combined 

 forces of the attraction of the body and the re- 

 sistance of the air. 



1 he size and form of the charged body also 

 exerts a powerful influence over this equilib- 

 rium of forces. Thus the electrical fluid is 

 found to become more concentrated at the 

 smaller end of an electrified body, and conse- 

 quently the electrical atmosphere will be 

 found to be more widely difl^used at that part, 

 as in the annexed figure. 



Fig. 40. 



When the air is cool and charged with wa- 

 ter in the form of vapor, it ofl^ers less resist- 

 ance to the electric fluid than when more 

 heated and dry, consequently the electrical 

 atmosphere will diffijse itself wider in the 

 former tiian the latter state of the air. Hence 

 the electrical phenomena of a thunder ftorivi 

 are generally more intense in very hot and 

 dry weather. 



Now we may suppose that the conductor 

 begins to act upon the electricity of l!;e 

 charged body so soon as its point enters t,::e 

 electrical atmosphere. But I have sliown ;l;;!t 

 this atmosphere is very variable in itse.xtent, 

 consequently the distance at which tlie rod 

 can operate is equally variable. Hence, as 

 before stated, no such distance can be as- 

 signed. 



I will now endeavor to answer the inquiry 

 of 1. T. S. agreeably to the foregoing illus- 

 trations. 



Suppose an electrified cloud to be spread 

 over the building, fig. 41, at such an elevation 

 that its electrical atmosphere shall fall within 

 tlie reach uf the rod at a, it must be obvious 

 that another rod at b would perform an equally 

 clficitnt part with the other in disarming the 

 cloud and protecting the building. ThosauK^ 

 will hold true of any additional number of 

 rods which might be put up. But we cannot 



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