W. H. PRATT LIGHTNIXG PHENOMENA AT BLACKHAWK. 93 



he was found lying there, having- apparently fallen lifeless without 

 the smallest struggle. On the south side of that tree, and about five 

 feet from the ground, was a limb, two inches thick, extending out di- 

 rectly over the back of the horse as he stood there. The under side 

 of this branch, for a few inches in length near the body of the tree, 

 was torn to fine shreds in a manner which plainly showed the same 

 ouftcard explosive action. No other part of this tree was injured, 

 and none of the other trees were at all disturbed. 



At S a cow was tethered to a stake in the grass ground, but entire- 

 ly uninjured. 



I do not propose to advance any theory, but the idea suggested to 

 my mind by these phenomena is something like this : Suppose the 

 molecules of a body of wood, or any other sul)stance, to be by some 

 cause forced out of their normal position of equilibrium and thus held 

 in a state of extreme tension, or, to illustrate, suppose millions of mil- 

 lions of spiral springs in each cubic inch, and each wound up tightly 

 and strained to the uttermost and held so. Then, suppose this strain 

 to be released instantaneously and each spring, or each molecule, to 

 return to its normal position with a movement which, though occupy- 

 ing but an infinitesimal fraction of a second, should, during that time, 

 have a velocity of thousands of feet per second. It is quite conceiv- 

 able that such intensely rapid molecular motion might so disturb the 

 intermolecular relations while passing from the abnormal to the nor- 

 mal position, as not merely to overpower but to neutralize and sus- 

 pend cohesion. Such an extreme velocity of motion in the mass, rep- 

 resenting an immense amount of energy, instantaneously arrested, 

 would be converted into a corresponding amount of some other form 

 of energy. 



It seems to me that we have a rude analogy for this, enough, at 

 least, to aid in the conception of such conditions, in the familiar case 

 of " Prince Rupert's drops." In these, as is well understood, the 

 molecules of the glass are in a state of such high tension that though 

 — undisturbed — they will maintain their abnormal position in relation 

 to each other for any length of time, yet, if we disturb it by making 

 ever so small a fracture, breaking off the extrerhe point, the whole 

 are instantly released, and, with suddenness amounting to an explo- 

 sion, the mass is completely disintegrated, the molecules part com- 

 pany, and the whole is reduced to a powder. 



In this view, a lightning "stroke" is such only in the sense of a 

 shock, a suddenness of action or change. A person is "struck" by 



