6 THE TREE BOOK 



time, electricity plays a very important part in- 

 deed in the clouds. It holds the little vapor 

 particles apart, and the clouds float hither and 

 yon till the electricity gets a chance to escape. 

 This is where the trees sometimes help. 



A forest of trees, with their multitude of tiny 

 branches, is like so many lightning-rods, pre- 

 senting their millions of points both for the dis- 

 charge and absorption of electricity. When the 

 cloud reaches the damp stratum of air above the 

 trees, its electricity is attracted by the numerous 

 vegetable points below; the electricity eagerly 

 seizes the conductor offered; the particles of 

 vapor rush together, and the whole comes down 

 in a copious shower. Thus, trees may be the 

 direct agents in producing rain. 



As there is a layer of moisture above the 

 woods, so there is a layer of dry, heated at- 

 mosphere above the plains. Sometimes a rain 

 cloud, floating toward the dry section, is drawn 

 out of its course — attracted by the stratum of 

 damp air, above the woods along a river valley, 

 and this section gets the rain which the plains 

 really need far more. Again a dense electric 

 cloud will pass over our heads, without shedding 

 a drop of rain, until it reaches the ocean, when 

 the cool, moist air above the waves, acting as a 

 conductor, causes the cloud to part with its elec- 



