THUNDER AND LIGHTNING 



IN lands devoid of volcanoes thunder-storms provide the 

 most impressive suggestion of the primal fiery chaos out of 

 which the earth as we see it was evolved. Great thunder- 

 storms in England are rare so rare that one may hardly be 

 seen in a lifetime ; and lesser disturbances very frequently 

 follow the same paths, while the country outside them is 

 comparatively immune. Both river valleys and ranges of 

 hills attract the summer type of thunder-storm which is 

 commonest in English latitudes ; and half a dozen storms 

 may travel in a summer along these thunder zones, while 

 the country five miles away may remain sunny and waterless 

 on each occasion. Thunder-storms thus have a double 

 aspect ; for although they are alarming and dangerous when 

 severe, they often bring welcome rain in a time of drought. 

 Partial thunder-rains have often saved the hay or root-crop 

 in a single parish, or even on a single farm, while a mile 

 away the crop perished or became practically worthless for 

 want of moisture. 



Thunder-storms are produced by a violent contrast in the 

 temperature of neighbouring masses of air ; and although the 

 air itself is invisible, we can often see the conflict traced in 

 the shape of the thunder-cloud. The towering and rounded 

 white clouds called ' wool-packs ' or ' thunder-pillars ' mark 



