384 POPULAR SCIENCE MONTHLY. 



north and south to all points in the east between north and south, 

 making all sorts of combinations, accelerating in speed, slowing up, 

 sometimes standing still seemingly, but yet progressing surely, certainly, 

 inevitably to the east. 



The anti-cyclone, judging it wholly from its invariable surface 

 effects, which can be seen day after day on the United States Weather 

 Bureau's daily maps, is essentially a down-draught eddy or center of 

 dispersion for the winds; an area where the barometric pressure is 

 above the normal (Chart No. 1). The cyclone, also invariably, so far 

 as the surface levels of the atmosphere go, is an up-draught eddy, a 

 center of wind concentration; an area where the barometric pressure 

 is below the normal (Chart No. 2). When it is remembered that the 

 winds circulate outward from the high pressure center of an anti- 

 cyclone spirally, from left to right, clockwise, while the winds move 

 into the low pressure of a cyclone spirally, from right to left, counter 

 clockwise, some idea of the simplicity of weather causation is gained. 

 Eemembering also that, by reason of the descent of relatively cool, dry 

 air and its dispersion, the polar anti-cyclone is the cause of clear and 

 cool weather phenomena, while by reason of the rushing in of warm, 

 moist air on one side, its expansion and cooling as it rises, and cool, dry 

 air on the other, the cyclone is the seat of storm phenomena, the first 

 primary lesson in American weather is over. 



Through a failure to grasp the greater synthesis of the weather, 

 terminology and local storm differentiation have naturally become hope- 

 lessly muddled in the newspapers, though here the difficulty of grasp- 

 ing the facts is even less than in the first issue. The cyclone is the 

 center of rhetorical disturbance, and inky clouds of misuse and abuse 

 gather about it, since, as a parent of storms and as a weather-breeder 

 of no mean type, the cyclone plays the dramatic leading role in Ameri- 

 can meteorology. It is not only itself capable of great development of 

 storm energies in the winter, early spring and late autumn, but in its 

 milder summer moments is particularly likely to be the parent of 

 specific local disturbances. With one of these, the tornado, it is 

 identified popularly by the newspapers, which, in spite of all explana- 

 tion on the part of the Weather Bureau, have not yet seen the absurdity 

 of applying to a secondary phenomenon, insignificant in size compared 

 with -the primary eddy, the name of the general disturbance. The 

 cyclone, sweeping along with warm, moist weather in front, clear and 

 cool weather in its rear, attended by a general rain, and in its sphere 

 of influence covering a dozen States or more, surely may be separated 

 from the local tornadoes, which, though destructive and terrifying, are 

 but mere local incidents in the parent circulation. This is so 

 markedly shown in the weather map of March 27, 1890, that, once 

 seen, it is incomprehensible how error can so hold its own (Chart No. 3). 



