-1859] WRITINGS OF JOSEPH HENRY. 371 



sented by yl 5 C in Fig. 20, and let another cloud D E Fhe 

 situated between the above-mentioned cloud and the earth. 

 Let the two clouds be supposed to be charged with the same 

 kind of electricity, and both positive. Let us further sup- 

 pose that the lower cloud D E F he only so far from the 

 earth as to be just beyond the striking distance, and the 

 man, cart, and horses to be at L, under the part E of the 

 cloud which is nearest the earth. Now let the remote end 

 C of the upper cloud approach the earth within striking dis- 

 tance, and suddenly discharge itself at G. The effect which 

 would be produced by this arrangement, at the moment of the 

 discharge Cc G, will be understood bj"- considering the condi- 

 tion of the electricity in the two clouds, and in the earth a 

 moment previous to the discharge. Both clouds being posi- 

 tive, the two will act upon each other by repulsion, the free 

 electricity of the lower cloud will be driven down into its 

 lower surface, and will be accumulated particularly in the 

 point E nearest to the earth. The ground underneath the 

 lower cloud, and more especially at L, where the distance is 

 least, will become highly negative. The natural electricity 

 will be driven down into the ground by repulsion, and will 

 be retained there as long as this condition remains, but when 

 a discharge takes place at the point C G, if the cloud J5 be a 

 good conductor, the repulsion at A and D will be suddenly 

 removed, and the natural electricity of the earth will return 

 with a rush to the surface and pass beyond its point of 

 natural equilibrium, as in this case into the man and horses. 

 The loud report was caused by the discharge from D to A, 

 which was invisible to the eye of the spectators on account 

 of the density of the lower cloud. 



An experimental illustration of the effects produced in this 

 case may be readily furnished by charging two conductors, 

 arranged in the relative position of the two clouds. At the 

 moment a spark is drawn from the end C a discharge is 

 observed at D A. The death of the lamb and the shock 

 felt in the foot of the woman were both produced according 

 to this view by the sudden rushing up of the natural elec- 

 tricity of the ground, when the repulsion in the upper cloud 

 was in part diminished by the distant discharge. 



