114 ANNUAL EECORD OF SCIENCE AND INDUSTRY. 



plain why conducting objects, isolated from the ground, but 

 placed to the southwest or the northeast of large conducting 

 objects that are in communication with the ground, should 

 be exposed more frequently to lightning strokes. He termi- 

 nates his communication by the remark that the known 

 modifications in the value of terrestrial magnetism conse- 

 quent upon the movement of the planets, are analogous to 

 those changes that the thunderclouds produce upon the 

 electrical condition of points on the earth's surface. 6 Z?, 

 1873,1394. 



THE ORIGIN OF ATMOSPHERIC ELECTRICITY. 



The existence of electricity in the atmosphere, even when 

 no lightning is visible, was first shown in 1752 by Delor. 

 Numerous observations have shown since that day that this 

 electricity is always positive when the heavens are clear, 

 and in general the intensity of the electricity increases with 

 the elevation of the point on Avhich the observer stands 

 a rule which holds even for observations made in balloons. 

 The annual periodicity of the intensity of the electricity was 

 first demonstrated by Beccaria. The daily periodicity was 

 proved by Schubler. Both of these periods have, apparent- 

 ly, some connection with the vapor in the air. The varia- 

 tion of the intensity of the electricity with the geographical 

 position of the observer is, as yet, but little understood, al- 

 though the observations seem to indicate that the intensity 

 decreases as we go from the equator toward the poles ; at 

 least this may be the case for the lowest strata of the at- 

 mosphere. The origin of atmospheric electricity was sought 

 for by Lavoisier and Laplace and Sir Humphrey Davy, who 

 attributed its origin, in great part, to the combustion taking 

 place every where on the earth's surface. Volta and Saus- 

 sure advocated that it arose from the process of evaporation. 

 Pouillet pointed out the influence of the processes of vegeta- 

 tion, but Reich demonstrated that neither gradual evapora- 

 tion nor the processes of vegetation develop electricity, and 

 that these processes, therefore, could not be the origin of the 

 atmospheric electricity. Peltier subsequently developed a 

 new theory, according to which our atmosphere of itself pos- 

 sesses no electricity, but that the solid earth is negatively 

 electrified, and, although the quantity be invariable, yet the 



