672 WILLIAM HALLOCK 



discharges of such varying force were scattered over an area of 

 perhaps thirt}^ to forty feet square, the more violent ones being 

 within twelve or fifteen feet of each other, Upon examining the 

 point at which any one of these discharges struck, a white incrus- 

 tation was apparent upon the rock, as if white paint had either 

 been spattered about or had been spread over as a rough, branch- 

 ing, straggling line. These white incrustations, in some cases, 

 could be traced for a foot or more down into the cracks between 

 the rocks. In other cases, they were mere spots. These white 

 streaks were, undoubtedly, the paths along which the electricity 

 ran, and a superficial examination showed that the white was due 

 to an incipient fusion of the surface of the rock. Unfortunately, 

 it was not practicable to get satisfactory photographs of these 

 markings or to bring in large specimens. Small specimens, how- 

 ever, were brought in, and have been subjected to investigation. 

 The probable explanation of the scattering discharge of this 

 particular lightning is to be found in the extreme dryness of the 

 ground. The cloud charged with electricity would, of course, 

 induce the opposite kind in the trees and rocks immediately 

 beneath it. Then, when the discharge came, it was necessary 

 that each prominence should discharge to the cloud individually , 

 because the ground connecting the different prominences was 

 too poor a conductor to rapidly collect the quantities of elec- 

 tricity and discharge them through a single point, as is usually 



the case. 



William Hallock. 

 Columbia University, 

 New York City. 



