TRANSACTIONS OF SECTION A. 423 
Average Temperature Gradients. 
Ground 500 750 | 1000 1250 1500 1750 
aa to 500 | to 750 | to 1000 | to 1250 | to 1500 | to 1750 | to 2000 
0-41 0°43 0°37 0°41 
Summer, A.. 0:98 0°82 6 
C. 2 0°66 0°56 0°50 0°45 
5 
8 
0 
“5 ie 1:03 0°87 0: 
Winter, A. . 0°60 0°53 0 
eae 0°73 0°69 0 
0°41 0°36 0°40 0°38 
0°66 0°61 0°61 0°52 
Winter and Summer.—The above figures show that near the ground, both 
under anticyclonic and cyclonic conditions, the temperature gradient is larger in 
summer than in winter. 
Day and Night.—During the summer of 1909 ascents were made throughout 
the twenty-four hours. The temperature gradient near the ground is larger in 
the daytime than at night. 
Average Temperature Gradients. 
Ground 500 750 1000 1250 1500 1750 
Shes to 500 to 750 | to 1000 | to 1250 | to 1500 | to 1750 | to 2000 
FF) 
Day . 5 0:93 0-90 0°66 0°50 0°49 0°47 | 0:45 
Night . A 0°50 0°62 0-60 0-48 04 eas | 0°51 
Diurnal Variation.—The temperature gradient near the ground shows a well- 
defined maximum at about 1 p.m. or 2 p.m. which is not appreciable above 
1,250 m., e.g., the temperature gradients in summer are as follows :— 
Height 7am. |9a.m.| 11 a.m. |1p.m.|/3 p.m.|5 p.m. 7 p.m. /9 p.m. 
335 to 500. tt 0:90 0°88 0-99 1:00 | 1:14 | 0°85 | 0°56 | 0°69 
500 to 750... 0°64 0-78 | 0°83 097 | 0°95 | 0°86 | 0°67 | 0°59 
Variation with Wind Direction.—The temperature gradient to 1,000 or 
1,250 m. is small for S., S.E., E. winds; and more or less constant, but larger, 
for the other directions. The average gradients for §., S.E., E. winds are com- 
pared below with those for other directions :— , 
1000 1250 
Ground | 500 750 | : 
to 1250 | to 1500 | to 1750 | to 2000 | 
| | 
to 500 | to 750 | to 1000 
0°52 0°46 
0°48 0°52 
Other directions 0-9 
8.,8.E.,E. . 06 
Temperature Gradient, °C. 
Height ——— Se: 
18° | 14° 10° 6° ge |) 8° 
Ground to 500 _ . x 1:13 
500 to 750 . P = 0-94 
Temperature Inversions and Zero Gradients may be taken to represent simply 
extreme cases of small gradients. They generally occur, as the foregoing would 
