THUNDER AND LIGHTNING 213 



helps to account for the large number of poplars which are 

 smitten. The explosive force of the lightning-flash is often 

 astonishingly shown by the distance to which fragments of 

 wood are hurled. When the flash passes down the trunk 

 the wood is rent into long strands, and the tree is rather 

 burst than merely struck or gashed. The layer of sapwood 

 is shattered, so that a tree severely struck often dies in the 

 course of the next year. 



The gloom of a thunder-storm by day is often one of its 

 most appalling features, especially to animals and birds ; but 

 the play of the lightning is seen most perfectly at night. 

 Then the spectacle is more beautiful, and less awful ; we see 

 not only the overmastering flashes, but every crackle and 

 shimmer of the electric discharges ; and distant nocturnal 

 storms are among the most attractive of all the year's dis- 

 plays. For all its violence at close quarters, the sound of 

 thunder does not carry more than twelve or fifteen miles ; 

 and the play of lightning at such a range by night may be as 

 easily visible as though the storm were in the next field. A 

 thunder-storm is a supremely beautiful spectacle when, as 

 sometimes happens, it rages in a mass of cumulus cloud 

 sailing at a good round pace through a clear sky lit by a 

 large moon. Constant flashes illuminate perpetually varying 

 lines of cloud, silhouetted in dark curves against its glow, 

 and delighting the eye by the magnificence of their airy 

 scenery. Beneath the Surrey Downs we have seen such a 

 storm pass silently in a July night, apparently following the 

 crest of the hills not three miles away, though actually it was 

 five or six times as far distant, and drenching London with 

 torrential rain. The so-called summer lightning that flickers 

 after dark in a sky often clear of cloud is the signal of 

 storms still more remote. With a local canopy of cloud near 

 the horizon to reflect it, lightning can be seen in this way at 



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