LIGHTNING AND RAIN. 299 



be the true and only cause of evaporation, its 

 condensation and precipitation can be effected 

 only by the evolution of the same agent. During 

 winter, the quantity and elastic force of vapour 

 in the atmosphere are comparatively low in the 

 middle latitudes, where it is condensed gradu- 

 ally on meeting with colder air. During spring, 

 evaporation augments with increase of tempera- 

 ture, when masses of warm and cold air often 

 meet, causing frequent showers of rain, and 

 sometimes hail ; still without much thunder and 

 lightning. But during summer, when the tem- 

 perature becomes tropical, and the atmosphere 

 saturated with highly elastic vapour, we have 

 tremendous explosions of thunder and lightning, 

 with rapid precipitations of rain and hail. Cor- 

 responding with the temperature of the torrid 

 zone, and the amount of evaporation, thunder 

 storms occur almost daily during the rainy 

 season, on the coasts of India and S. America. 



One of the most prominent errors in regard to 

 the natural history of lightning, is the prevalent 

 notion that it collects around the surface of clouds, 

 as if they were solid insulated conductors ; and 

 that when it becomes accumulated to a certain 

 extent, it darts from one to another. Nothing 

 could be more in opposition to all analogy and 

 experience. Clouds are only banks or strata of 

 moisture, while it is universally known that elec- 

 tricity cannot be accumulated in a moist atmo- 

 sphere, that it is diffused and dissipated by 



