294 PROCEEDINGS OF THE AMERICAN ACADEMY 



tween the quantity of electricity occasionally collected in the 

 atmosphere, and that which could be held by the conductor of 

 the largest electrical machine, had not, certainly, been exagger- 

 ated in the remarks already made. " It should not be forgotten, 

 however, that the conductor, no less than the cloud, might be 

 raised by the feeblest electromotive power to its state of maxi- 

 mum electrical tension, and that this maximum was higher 

 for the conductor than for the cloud, on account of the dimin- 

 ished density of the air at the place where the cloud existed. 

 If, therefore, the electrical attraction between a cloud and the 

 earth is great, it must be the result, not of the surpassing ten- 

 sion of atmospherical electricity, but of the large surface which 

 this tension covers ; and the extent of surface must be sufficient 

 to overcompensate for the unusual distance through which the 

 electrical forces act. Although it may be questioned whether 

 the forces thus considered are adequate to produce the terrible 

 mechanical movements which accompany the tornado, they 

 are doubtless competent to draw down the cloud in the form 

 of an inverted pyramid towards the earth's surface. Here the 

 agency of the electrical tension may be supposed to terminate, 

 and that of the quantity to begin to play its part ; and as this 

 quantity may be exceedingly great, the effects of its discharge 

 from this cone of cloud pointing to the earth may, in the same 

 proportion, surpass the feats of the electrician in his experi- 

 ments with the machine of his own invention. In whatever 

 way the motion of the air which is observed at the time of 

 the brush discharge from the pointed conductor is explained, 

 that motion, we may admit, will be multiplied into the force 

 of a hurricane, if it corresponds with . the great amount of 

 electricity which has accumulated in the prime conductor of 

 our planet. A reason for the fact that the electricity seeks its 

 way to its resting-place in the solid earth by the thunderbrush, 

 and not by the thunderbolt, may be found, in one instance at 

 least, in the extraordinary aridity of the earth's surface, in 

 consequence of which that surface could not receive and dis- 

 tribute the charge from one point, but each spot drank its own 

 portion from the inverted cup as it was handed along." 



