450 F. H. Bigelow — Inversion of Temperatures in 



calm area or one of variable winds, the vapor contents being 

 cooled by mixture with the lower temperatures and therefore 

 precipitated ; at the same time with the counter flow, right 

 hand deflecting forces generate a couple of gyration (See U. S. 

 daily weather maps, Tuesday, March 27, and April 7, 1894, for 

 illustration), which develops somewhere along the axis of 

 encounter a cyclonic whirl, due almost exclusively to horizontal 

 transportation, the vertical movement being a subordinate 

 action ; indeed the rapid whirling is a symptom of the lack of 

 vertical motion, the escape of the air at the top of the vertex 

 in the general eastward current being a source of loss of gyra- 

 tory energy; rainfall accompanies a low area on the side 

 chiefly of greatest cold, or where the oceanic supply can first 

 meet with colder air, and is not a cause of it ; tornadoes, 

 thunder storms, the thin band of rain and other phenomena, 

 are secondaries to the counter flow from the two high sheets, 

 are located along the axis, and derive their power from the 

 force of gravity acting on the primary denser high area masses. 

 The synchronism of the magnetic curve is evidently, from day 

 to day, the efficient governor in the succession, this changing 

 in type with the inversion of the system. The difference 

 between the North American and the Siberian systems is a 

 marked increase in the number of cyclones in North America, 

 which cannot be accounted for by geographical conditions. 

 The presence of the magnetic polar system on the American 

 continents is, however, a sufficient source of differentiation. 

 The peculiar system of feeders in the United States is due to 

 the existence of long troughs between successive High areas, 

 along the axis of which the cyclones move eastward and north- 

 ward ; while the Siberian High area, thrown up by the general 

 circulation, is not broken into smaller masses by the magnetic 

 variable intensities. The interplay about the "origin" is that 

 of the discharge of the polar High belt across the Low belt, 

 the tendency of the Pacific High to join the Polar High, the 

 drift of the High areas east, partly along the Low belt, and 

 partly into the southern High, and also between them as if in 

 doubt which system to join. The interplay of these several 

 systems adds to the complexity of the weather of the United 

 States, and renders the art of forecasting very difficult to 

 acquire. 



Much light is, however, thrown upon these problems, by the 

 possession of the true solar period of rotation, the form of the 

 intensity curve, and the fact of its sudden reversal at certain 

 times. This has occurred recently, on Dec. 3, 1893, Jan. 21, 

 1894. Attending these reversals are stagnations of movement, 

 the transition from the polar to the midlatitude circulation, the 

 passage from one hemisphere of the sun to the other, and 



