144 ROCHESTER ACADEMY OF SCIENCE. [May 9^ 



multitude of ways, and the study of thunderstorms as a practical 

 exemplification of the action of these forces becomes increasingly 

 interesting. The idea based upon certain laboratory experiments 

 which ascribes such storms to the storing up of positive electricity in 

 the upper atmosphere through the evaporation of a saline solution 

 such as are the waters of the ocean, and the discharge of this elec- 

 tricity disruptively in the case of thunderstorms and quietly in the 

 case of auroras is utterly inadequate. If this be the proper explana- 

 tion there must have been an enormous amount of such evaporation for 

 a curiously limited interval on Feb. 13th, 1892, and exactly twenty- 

 seven and one- quarter days later, it must have begun again in a very 

 strange way in order to account for the world-wide magnetic storms 

 and splendid auroras of those dates. The evaporation theory cer- 

 tainly fails to account for the facts in such a case as this, and is 

 equally deficient as an explanation of widespread outbreaks of 

 thunderstorms. 



The atmospheric conditions to which thunderstorms are inci- 

 dental present peculiarities that require examination in detail. Upon 

 any weather map there appear areas of high barometer termed anti- 

 cyclones, from each of which air currents proceed outward in every 

 direction until they meet the corresponding outflow from adjacent 

 anti-cyclones. In a belt along this line of meeting, storm action is 

 most severe. Here there is conflict of winds, air strata at different 

 altitudes moving in different directions with sudden shifts, and rapid 

 changes of temperature and more or less cloudiness and precipitation. 

 Along this line are eddyings and whirls some of which reach the 

 dimensions of the rotary storms designated cyclones. In the midst 

 of this turmoil, but not at the seat of lowest pressure thunderstorms 

 are most apt to occur. The ordinary theory is that all this atmos- 

 pheric commotion is due to the agency of heat and gravitation 

 modified somewhat by the deflecting force of the earth's rotation, and 

 that the thunderstorm is generated on the spot and is not due to any 

 form of induction from the sun. 



It may prove t(?be advantageous to examine this theory some- 

 what in detail. According to this view masses of air warmed by the 

 sun's rays or by condensation of aqueous vapor and liberation of 

 latent heat, as the case may be, are supposed to acquire buoyancy so 

 as to rise in such manner as to permit the air from surrounding local- 

 ities to gravitate into the place thus made vacant with the velocities 

 and in the directions shown on the weather maps. In order that this 

 theory may be justified, it is necessary that there be evidence of the 



