AND LIGHTNIJiG CONDUCTORS. 



77 



amplitude of imagination not usually displayed in profound 

 philosophical contemplations; considering also that the 

 hypothesis implies not only an identity in the material and 

 structure of the bodies operated on, but also an invaria- 

 bility of influence and action, irrespective of distance, it 

 can be viewed in no other light than as one of the boldest 

 steps in the advance of fact hitherto recorded in the history 

 of science. Such, however, is the only basis on which the 

 doctrine of pointed lightning-rods was originally founded, 

 and such alone is the source of all the reputation they have 

 acquired, and of all the faith that has been placed in them 

 for protection, from their first introduction to the present 

 day.* Nevertheless, too much praise cannot be awarded 

 to Franklin for this noble attempt to enlist the principles of 

 science into the service of humanity ; and although, from 

 the then infantile state of atmospheric electricity, and the 

 consequent want of information necessary for affording cor- 

 rect notions respecting the influence of thunder-clouds on 

 pointed conductors at the earth's surface, and the pre- 

 liminaries requisite to give direction to strokes of lightning, 

 it must be acknowledged that the idea of protection from 

 lightning by means of vertical metallic rods originated with 

 that eminent philosopher. Had experience in atmospheric 

 electricity been more ample and varied at the time Franklin 

 projected his lightning conductors, he would have known 

 that the atmosphere is replete with the electrical element, 

 independently of the presence of cloud, under every cir- 

 cumstance of serene weather, and in every season of the 

 year ; and that those clouds which hang within reach of a 

 kite-string, as well as those which drag upon the ground, 

 are invariably highly charged with electro-positive action ; 



* It would appear from Franklin's own account of his experiments with 

 pointed bodies, such as sharp pins, that the distance between the electrized 

 body and the point, never exceeded much above 12 inches. — See his 

 Ijetterf, or Fhilosophicul Papers. 



