DYNAMIC METEOROLOGY. 3()3 



eight wbere the last was more easterly tlinii tlie first, as opposed to three 

 and tive cases, respectively, where the movement was toward the north 

 or west. 



Series (c). — For the maxima in this series, Loomis remarks that appar- 

 ently, by reason of small variations of the pressure of the air, the cen- 

 ters appear to show rapid movements to and fio, but that in general, in 

 the fourteen cases where the isobar of 31 inches continued for at least 

 two days, the jiosition on the last day did uot differ materially from that 

 on the first. 



The relative size of the barometric maxima in the United States was 

 investigated by Loomis for the maxima of Series {a) (Loomis Table xii), 

 with the assistance of the charts of the International Bulletin, but only 

 since October, 1877, because the weather charts for the United States 

 only did not cover enough ground to fully present these extended phe- 

 nomena. The mean value of the smallest diameters of these regions of 

 extraordinary high pressures measured between the isobars of 7C2 milli- 

 meters is 2,587 miles, which is equal to the width of the American con- 

 tinent at 40° north latitude. The mean distance of the centers of low 

 I)ressures from the centers of maxima was 2,371 miles on the east side 

 of the maxima and 2,381 miles on the west side ; the value of the lowest 

 isobars in these measurements was 29.19 inches = 741.4 millimeters on 

 the east side, and 29.57 inches = 751.1 millimeters on the west side; so 

 that therefore the gradient was twice as great on the east side as on 

 the west side. If we reduce the adopted superior limit from 30.85 to 

 30.4, we find that the mean diameter of the maxima between 1877 and 

 1884 that rise above this limit amounts to 1,40G miles, and that the ba- 

 rometer in these is on the average 0.40 inch above its normal value. 

 For the maxima above 30.85 these values become, respectively, 2,587 

 miles and 0.75 inch. Since 0.75 : 0.40 = 2,587 : 1,380, therefore the 

 diameters of the maxima are approximately i)roportional to their alti- 

 tudes measurt^l from the normal value. 



iSeries {b). — The mean diameter of the maxima of this series for which 

 the isobar 7G0 millimeters is taken, is at least 2,740 miles, therefore 

 larger than in the United States. The lowest isobar on the west side 

 was on the average 739 millimeters — only in two cases was it less than 

 730 — whereas this is a frequent case on the Atlantic Ocean; therefore 

 here also an uncommon high pressure does not imply a remarkably low 

 l)ressuie in the neighborhood. The mean distance of the center of high 

 pressure from that of low pressure on the west amounted to 2,280 miles, 

 which indicates a somewhat greater gradient on the Euroi)ean side of 

 the ocean than on the western or American side. 



Series (c). — The mean diameter of the maxima of this series is 3,800 

 miles in the north-south direction under 55"^ ol' north latitude, and 

 4,900 miles in the east west din-cttion. 



The temperature relations of tlie baro;netric maxima are quite thor- 

 oughly investigated by Loomis. In tlie cold season of the year the 



