ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 337 



rapidly to descend, so as to be again available. The hydrogen balloon 

 might, for instance, carry a small vessel containing a substance which 

 would combine with the oxygen and with the vapor of the air at an 

 approximately known and arranged rate; the increased weight of the 

 contents would reverse the ascent at a roughly calculated height, and, 

 except with strong winds, the balloon would descend at no great dis- 

 tance. In calm weather its motion could be watched with a telescope 

 and its approximate height noted. Intelligent persons in towns and 

 villages should previously be instructed to secure the descended bal- 

 loon and to take readings. Schoolmasters in France have received 

 such instructions. 



It is probable that the condition of air immediately preceding torna- 

 does, cyclones, and blizzards, and thunderstorms or heavy rains would 

 frequently be of sufficiently remarkable character to give ground for 

 generalizations from balloon records by which the advent of these 

 phenomena could be foretold. 



ELECTRICITY, CLOUDS, AND RAIN. 



The connection of electricity with the formation of rain, snow, and 

 hail requires much fuller investigation than it has yet received, and 

 research in this field is sure to yield interesting results. The upper air 

 is positive, the lower often negative, and the almost invariable neces- 

 sity for two or more layers of clouds for the production of anything 

 more than misty rain over level ground seems to point to an almost 

 invariable coexistence of oppositely electrified clouds in the formation 

 of heavy rain. Heavy showers and snowstorms always show a large 

 development of free electricity, but of course this maybe merely a con- 

 sequence of the agglomeration of the drops, and in no important degree 

 a cause of the precipitation. In the heavy clouds of showers there 

 seem to be generally several zones or areas of opposite electricities. 

 The observations on Pikes Peak show the large development of free 

 electricity in the rain, and hail, and snow formed at great altitudes. 

 Howard deduced from Eeed's observations that snow and hail unmixed 

 with rain are positive almost without exception. Probably if the snow 

 and hail could have been intercepted in the upper air, it might have 

 been said "without exception." On one occasion, when "a most awful 

 darkness filled the atmosphere" and some rain fell mixed with hail, the 

 positive charge became "as strong as it could possibly be." 1 



Experiment on the electricity of clouds, showers, etc., does not seem 

 to have been continued in recent years, though much might be learned 

 from it in connection with the other conditions of weather. On the 

 other hand, laboratory experiment on the electrification of steam, of 

 smoke, and of small drops has led to most interesting results. An 

 electrified rod, at a few thousand volts, with brush discharge, in a 



1 Phil. Trans., Vols. XXXI, XXXII. 

 SM 95 22 



