ATMOSPHERIC ELECTRICITY. 28/ 



lightning by his kite and a key, is the actual discovery due. We have 

 already detailed the circumstances (page 206) and need not repeat the 

 account of the experiment. 



Of course the American philosopher found numerous imitators, not 

 always with impunity. Professor Richmann was killed by the spirit he was 

 invoking ; Lemounier and Beccaria confirmed the theory that the air was 

 full of electricity ; while Du Saussure, from his investigations on the Alps,, 

 and Volta from the invention of the pile, are most famous in the history 

 of electricity. They applied themselves with much success to the investi- 

 gation of the electric condition of the atmosphere, of which the disturbances 

 called thunderstorms are the result. 



The amount of electricity varies in the atmosphere at different times 

 in the day and night. Towards midday and midnight the development is 

 generally greatest, and this fact will account for the prevalence of storms 

 during our hours of rest. Again, different kinds of clouds have different 



Fig. 287. Cirrus cloud. 



degrees of electricity, and of different kinds. Under certain conditions these 

 clouds will give forth lightning, and a storm will begin. The more clouds 

 the more globules, and therefore in summer, while there is more production 

 of vapour from solutions of salts, etc., we are more likely to have the storms. 

 We are most of us familiar with the mass of the " thunder cloud " rising in 

 the distance, light at the upper part, very dark below, and throwing out 

 tentacles like the octopus, coming up sometimes frequently, indeed 

 " against the wind," impelled by an upper current, or following the course 

 of a river, which is not unusual. Below, there is perhaps an army of thin 

 dark clouds. The nature and height of clouds have also a great deal to do 

 with the phenomena displayed. In general, storm-clouds are positively 

 electrified. 



Clouds are good conductors of electricity, and yet they may be so- 

 insulated by the dry air surrounding them that they will accumulate it ; and 

 when thus charged, if they encounter other clouds charged with opposite- 

 electricity, the opposing masses will attract each other until a discharge 



