1892.] VEEDER THUNDERSTORMS. 139. 



ilar to that apparent in the case of thunderstorms but not so strongly 

 marked. The conditions under which this localization of the aurora 

 occurs appear to be connected in some way with the sharp bending 

 of the lines of equal magnetic declination, as for example in the- 

 Adirondack region and Northern Maine and near the mouth of the 

 Ohio River. There are laws also governing the relative prev- 

 alence of these phenomena at different seasons of the year which 

 require further study from the point of view in regard to solar origint 

 here indicated. It is sufficient for the purposes of the present dis- 

 cussion to point out that there is such similarity in the behaviour of 

 auroras and thunderstorms in many important particulars as is con- 

 sistent with their having a common origin. 



Thunderstorms also exhibit definite relations to conditions of 

 atmospheric pressure that appear to be under the control of these 

 characteristic solar impulses. This may be shown in the following 

 manner : From the Daily International Weather Maps the location 

 each day of all centers of high barometer throughout the greater part 

 of the northern hemisphere may be obtained. Thus it may be shown 

 that at times these centers all suddenly begin to move eastward as if 

 by a common impulse. This happens under the precise solar con- 

 ditions that attend the aurora and thunderstorm. It is most pronounced 

 near the equinoxes when auroras also are at a maximum. Associ- 

 ated with it at all seasons there is marked intensification of storms. 

 This occasions the phenomenon of well-defined storm periods, but there 

 is not one universal storm. On the contrary, anti-cyclones as well as 

 cyclones are strengthened as atmospheric movements become more 

 energetic, so that during these very storm periods the weather in par- 

 ticular localities is much finer than common. 



Other evidence that the atmosphere as a whole is under the 

 control of induction from the sun, is to be found in the fact, that in 

 certain years when forces of this character are at a maximum, there 

 is a re-arrangement of the distribution of atmospheric pressure on a 

 grand scale. Anti-cyclones with greater heat in summer and greater 

 cold in winter, become more persistent in high latitudes, and cyclones 

 appear in the tropics, the belts of thunderstorms and auroras also- 

 descending to lower latitudes. In years of minimum on the other 

 hand there are anti-cyclones and drouths in the tropics and cyclonic 

 conditions in high latitudes, with cool summers and mild winters. In 

 such years drift ice comes down from the Arctic regions all winter. 

 Coincidently auroras and thunderstorms become less frequent and, 

 appear in higher latitudes. 



