HOWARD AND HOWARD aS) 
July and August are the wettest months. From November to April very 
little rain is received. The humidity is generally high and is lowest in March 
and April when it falls to about 60. 
Temperature. There is a well-marked cold season, December to Feb- 
ruary, when the minimum temperature remains in the neighbourhood of 50°F. 
In the hot weather months, March, April and May, the dry west winds are 
important agents in improving the aeration of the soil. The monsoon period 
June to September is hot and damp. After the middle of October, the tem- 
perature gradually falls till cold weather conditions set in at the end of 
November. 
Soil aeration. Periodical determinations of the amount of carbon dioxide 
in the soil atmosphere have been carried out in the Botanical area at Pusa by 
Mr. Jatindra Nath Mukherjee under the direction of Dr. Harrison, Imperial 
Agricultural Chemist, on cultivated and grass land for a period of eleven 
months. The results are given in Table Ii and in Plate I. A note by Mr. 
Mukherjee on the methods adopted is appended to this paper. 
Tas_e II. 
Percentage of COz in the soil gas from three different plots in the Botanial Area, 
Pusa, m 1919. 
Plot No. 2 : - 
Date and month when the ‘Plot N Grassed down Plot No. 3 | Rainfall = 
S255 ea eae ‘Plot No. 1 ‘all Surf inches since 
soil gas was aspirated Gr sania , but partially Surface | jt January 
and analysed sis ciara aerated by cultivated | isigaee 
F trenches 
13th, 14th and 17th Janu-* | ‘ 
ary 2 so 0-444 0-312 0-269 Nil. 
20th and 21st lebruary 0-472 0-320 0-253 1-30” 
21st and 22nd March 0-427 0°223 0-197 [eB 
23rd and 24th April 0-454 0-262 0-203 2-69% 
16th and 17th May 0-271 0:257 0-133 3°26” 
17th and 18th June 0-341 0:274 0-249 4-53” 
17th and 18th July 1-540 1-090 0-304 14-61” 
25th and 26th August p 1-590 0-836 0-401 23°29” 
19th and 20th September .. 1-908 0-931 0-450 30°67” 
21st and 22nd October... 1-297 0-602 0:365 32-90” 
14th and 15th November .. 0°853 0-456 0-261 32°90” 
These figures and the curves (Plate I), give a general idea of the soil 
atmosphere as regards ventilation in a year exceedingly favourable to the 
indigo crop. Aeration is at its best during the period of the west winds— 
March to May. After the monsoon has set in, the proportion of carbon dioxide 
