272 ELECTEICITY OF THE AIR ; LIGHTNING, 



trieity that can come from a thunder-cloud, during 

 its course through the metal to the earth. The 

 flash often strikes single trees that stand by them- 

 selves, because, rising, as they do, to a considerable 

 height, and sending'some of their roots deep down, 

 while others branch out in every direction through 

 the soil, they form true lightning conductors. 

 However, they possess but a low degree of con- 

 ducting power. Hence, to take shelter under them 

 is very dangerous ; for the electricity, not being 

 able to pass through them very swiftly, starts 

 across in part to other better conductors, such as 

 men and beasts, if any such be at hand, and 

 through them finds its way to the ground. 



Water, again, is a worse conductor than living 

 animals. The danger, therefore, of such being 

 struck by lightning, is always increased rather 

 than lessened by their being in the neighbourhood 

 of water. 



The case is altogether different with metallic 

 conductors of sufficient thickness. The lightning 

 will not leave them, even when the metal rod lies 

 directly upon wood or stone, not even if it should 

 pass through water, not even if one should grasp 

 it with the hand, since no other body can afford a 

 quicker passage to the electricity than does the 

 metal; only the chance of some fault in the 

 metallic connexion of the conductor, or of its fail- 

 ing to reach deep enough into the moist soil, may 



