ELECTRICAL APPARATUS. 299 



equally electrified whether it be solid or hollow, and if it be 

 hollow, the charge which it receives from any source of 

 electricity will be the same whether the shell of matter of 

 which it is formed be thick or thin. 



Fig 352. 

 Fig. 351. 



To demonstrate practically the distribution of electricity 

 on the surface of a conductor, the following apparatus was 

 contrived by Biot. A sphere of conducting matter, a, is 

 insulated by a silk thread, and two thin hollow covers, b b, 

 of brass or copper, are provided with glass handles, c c, and 

 correspond with the shape and magnitude of the conductor. 

 The sphere, a, is electrified, and the covers are then applied, 

 being held by the glass handles. After withdrawing them 

 from a, they are found to be charged with the same kind of 

 electricity as was communicated to a, which will be found to 

 have lost the whole of its charge, proving that it resided on 

 the surface only. 



But although electricity may be considered as confined to 

 the surfaces of bodies, its intensity is not on every part the 

 same. On a sphere, of course the symmetry of the figure 

 renders the uniform distribution of electricity upon it inevi- 

 table ; but if it be an oblong spheroid, the intensity becomes 

 very great at the poles, but feeble at the equator. 



Price, - $4.00. 



mounted on an insulated stand, $5.00. 



Faraday's Bent Electrical Conductor. (See Fig. 352, as 

 above.) Faraday's bent brass electrical conductor, with two 

 different sized balls at the extremities, for illustrating that 

 between conducting surfaces, the spark, in disruptive dis- 

 charges, is modified by the differences of the dimensions of 

 the discharging or receiving surfaces. Price, 81.75. 



