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"the charges on the cloud and earth becoming reversed, and these in turn discharge, 

 ^nd the reversing and redischarging is repeated over and over again, probably a 

 million times a second, until the energy of the stroke is exhausted. The stupendous 

 frequency of the oscillations makes the current travel almost entirely in the surface 

 layers of any conductor it may follow. 



Let us now study the conditions on the earth during a flash. Look at the 

 frontispiece, page 2. Immediately you say, " I never saw the flash spread out 

 like that either on the earth or in the cloud." Quite so. But if we return to our 

 ■electrical machine, and on the earth plate set a flat tin dish containing moist earth, 

 then wet one of our toy barns, set it on the earth in the tray and turn the machine, 

 we see at every spark innumerable ramifications of the flash spreading out over the 

 earth ! When the pressure breaks through between the cloud, and wet barn, the 

 charge from all parts of the earth-plate is in suoh a hurry to make its way up to 

 meet that from the cloud that it doesn't take time to follow all the irregularities 

 of the earth's surface, but jumps through the air from point to point, causing 

 sparks everywhere it does so, and the current reverses a few Imndred thousand 

 times during one flash. 



Thus we get the idea that when a stroke occurs the earth for hundreds of feet 

 around the object struck is in a highly electrified state and the electrification 

 changes from positive to negative many times during the flash. Hence there is 

 an alternating current to and from the object struck. This takes the path of least 

 obstruction, following conductors with least resistance and self-induction, and 

 often flashing or sparking from one to others near at hand. That's probably what 

 killed the cattle — the current jumped the space between them and the fence, and 

 the shock killed them. The death of the pigs is not so easily explained, as apparently 

 they were not close to any other conductor — and this is not an imaginary case. The 

 cut is from a drawing of Mr. West Dodd's, based on an instance that came under 

 his notice, where pigs were killed in an ojioii yard, although the stroke occured to 

 the barn some distance away. 



In an actual flash of lightning we do not see its ramifications on the earth 

 and cloud, but from our experiment with the toy barn and tray of earth we know 

 beyond peradventuro of a doubt that during the flash there are currents from all 

 directions to the earth focus, and by analogy we know the same must be true 

 in the cloud. Did not the flash so blind its observer for the instant, sparks between 

 conductors on the earth should readily be detected. So the earth- and cloud-rami- 

 fications in the frontispiece represent not streaks of liglit but alternating currents 

 of electricity and the lines of force which produce those currents. 



Why Newly Filled Baens Seem More Likely to be Struck. 



In this connection we should like to deal with a phase of the subject about 

 which there seems to be more or less misconception, viz., the claim that barns 

 newly filled with hay or grain are more frequently struck and burned than any 

 other class or condition of building. Whether such barns are more often struck 

 remains to be proven, but there is perhaps little donbt that if struck they are more 

 frequently burned than if empty. Most of us have no doubt honrd the old explana- 

 tion which runs something as follows: After the grain is stored in the barn it 

 '^ sweats" and gives off vapour to the air, and this nioistui-c ascending in a column 

 above the barn forms the easiest path for the lightning flash, for moist air is a 

 better condurtor of electricity than dry air. Some vary it by saying "gases" are 



