Mr. Sturgeon oti Electro-pulsations and Electro-momentum, 133 



magnetic wheels* which was soldered to an ii'on spindle and 

 put into rotatory motion by a wheel and band ; the points of 

 the wheel touching in succession a copper spring in connexion 

 with the positive surface, and thus producing a discharge at 

 every contact of the wheel and copper spring. 



When the two surfaces are connected by wii'es with two 

 basins of salt water, and the hands immersed one in each 

 basin, the effect experienced is precisely that of the discharge 

 of a voltaic battery. The discharges can be made in such 

 rapid succession as to prevent the sensation of distinct shocks ; 

 and if the process were to be concealed it would require some 

 experience to distinguish between the effects on the animal 

 ceconomy from this apparatus and those from a voltaic bat- 

 tery charged with acid and water. 



My views being so far verified, the next attempt was to 

 simplify the apparatus and make it more portable ; and as it 

 was readily seen that if one hundred pairs would charge glass 

 of considerable thickness, thinner glass might be charged by 

 fewer pairs ; this was done; and eventually the glass entirely 

 dismissed, and its place supplied with well-varnished Bristol- 

 board. These boards answer exceedingly well as a reservoir 

 for low intensities ; they may be coated to within an inch of 

 the edge all round, and placed upon their edges either on a 

 piece of glass or on a board properly prepared, and arranged 

 to any required extent like the plates of a voltaic battery, but 

 ■vvhen considerable intensity is wanted, it is better to use thin 

 glass. 



From these facts we learn that metallic surfaces of many 

 acres of extent may possibly be charged to a low intensity in 

 the interior of the earth, by having a thin intervening stratum 

 of inferior conducting matter sufficient to insulate from each 

 other their dissimilar electric surfaces. 



It may now be understood that the slightest accident which 

 would suddenly break through the insulation, such as the 

 sinking of a mass of metalline matter from one stratum to the 

 other, would cause a sudden rush of an immense ocean of the 

 electric fluid, which might be productive of subterranean light- 

 enings and tremendous explosions sufficient to shake an exten- 

 sive range of country on every side. 



Connected with the preceding facts there are others which 

 may be conveniently mentioned in this place, and which would 

 lead us to similar explanations of the causes of subterraneous 

 convulsions. Electric currents of considerable magnitude when 

 suddenly checked, or diverted to a new channel, produce a 



* [See Phil. Mpg., First Series, vol. lix. p. 241.— Edit.] 



