On the Effects of Lightning 249 



out of a chimney when fresh coal has been put on the fire. The 

 lightning flashed in all directions, great branches gave way, and 

 when the vapour cleared off there stood the pear tree, its trunk 

 a dazzling white : the lightning had taken the bark completely off." 



Without assuming that a tree struck by lightning is always 

 enveloped in a mass of luminous steam, we may feel certain 

 that it is surrounded by intensely heated air. It is thus that 

 we explain the scorching of adjacent objects. In the in- 

 stance of an oak struck and killed with lightning, which is 

 the subject of our plate, at p. 17, the adjacent oaks had their 

 branches killed through a wide radius. In the case described 

 last month, on p. 206, three fir-trees, of different species, which 

 stood round the one supposed to have been struck were all 

 quite killed, although there was no reason to suppose that any 

 of them had been struck. In several other instances the 

 writer has seen the boughs of adjacent trees killed apparently 

 by the globe of intensely heated air which surrounded the one 

 which was struck. 



On the Short Duration of the Flash and Explosion. 



Although it is probably impossible to realise the brevity of 

 the duration of the cause of these heated masses of air, it 

 must be remembered that the heat produced may last longer. 

 Its persistence will no doubt vary with the amount of moisture 

 in the air. It may be that in some cases the death of animals 

 (sheep, &c.) may be caused rather by the heat than by the 

 electric shock itself. 



The transitory nature of the lightning flash, and, at the 

 same time, its heat-producing capacity, is illustrated by the 

 statement that it may fail to ignite gunpowder, and yet melt 

 the gun-lock in which it was contained. It is often recorded 

 that it failed to set fire to hay or straw. Of this Flammarion 

 gives the following example : — 



"It was at Laplean in Correge. One day thunder fell on a grange 

 full of hay and straw, and covered with thatch, without setting it on 

 fire. Then it went to the sheepfold and killed seven black sheep, and 

 left the white alone." 



