WEATHEK BUREAU. 159 



cerning the movement of the atmosphere in that region. It is 

 apparent at the outset that the lower Hmit of the upper inversion 

 is not sharply defined, but that tlie air motion in the explored part of 

 that region, at least, partakes of, and probably is controlled by, that 

 of the lower levels of the atmosphere on wliich it rests. The observa- 

 tions of the ^^dnd velocity in tiie region of the upper inversion were 

 not conclusive in any respect, other than that the movement was 

 at times considerable, and again of rather low value, as on September 

 7, 1910, when, at Huron, S. Dak., winds at 3 to 11 kilometers altitude 

 (1.9 to 6.9 miles) averaged about 16 meters per second (36 miles per 

 hour). At the base of the upper inversion a wind of 18 meters per 

 second (40 miles per hour) was encountered; at 1,000 meters (3,280 

 feet) higher, the wind had increased to 32.5 meters per second (73 

 miles per hour). It continued at a high velocity up to 17,227 meters 

 (10.7 miles) and then suddenly fell off to 6.8 meters per second 

 (15 miles per hour). On another occasion, September 4, 1910, the 

 enormous velocity of 42.2 meters per second (95 miles per hour) was 

 found at the base of the upper inversion, and a still higher velocity of 

 48.5 meters per second (108 miles per hour) was encountered some- 

 what higher. Above this, liowever, the speed of the wind diminished 

 to zero. The ascension of the 4th was in a cyclonic area, while that of 

 the 7th was on the front of a strong anticyclone moving toward Huron 

 from the British northwest. 



Another interesting conclusion that may be drawn from the sound- 

 ing-balloon ascensions, and also from observations on high mountain 

 stations, is that the gyratory motion of the air characteristic of 

 cyclones at the surface and for some distance above, does not extend 

 far upward.* The movement of the upper layers, say above 10,000 

 meters (about 6 miles), as indicated from the drift of balloons that 

 ascended to that altitude, appears to be in three main directions, viz, 

 from west to east under normal conditions; from north to south, or 

 northwest to southeast, when anticyclones dominate the weather; 

 and from south to north, or southwest to northeast, when cyclones 

 control the weather. Perhaps a better way of expressing the idea 

 would be to say that the air currents are from some northerly direction 

 on the east side of anticyclones and fi"om some southerly direction on 

 the west side, and that under practically all other conditions the 

 drift ol the air in the very high levels is from west to east. 



One of the interesting facts brought out in connection with ascen- 

 sions in anticyclonic conditions is that the prevailing west winds of the 

 middle latitudes, formerly believed to extend in an unbroken stratum 

 from an altitude of about 5 kilometers (3.1 miles) to at least 16 

 kilometers (10 miles), are at times wholly suspended up to an altitude 

 of 12 Idlometers (7.5 miles). This fact is confirmed by observations 

 made on Pike's Peak, Colo., as will be referred to later. 



In 39 ascensions made under the direction of Prof. Rotch, in which 

 the altitude reached was 6 miles or over, 11 balloons landed almost 

 due east of their starting point, 22 landed south-southeast of their 

 starting point, and 6 landed north-northeast of their starting point. 

 It is not always, nor in the majority of cases, possible to tell from 

 surface conditions the direction the balloon \vill take. Sometimes, 



' Bigelow reached the same conclusion from a study of cloud observations. See Report Chief of Weather 

 Bureau, 1898-1899, p. 434. 



