182 
J. HOPKINSON—METEOROLOGICAL observations 
are corrected for this index error, rednced to 32° in accordance with 
the readings of the attached thermometer, and to sea-level. 
The thermometers are in a “ Stevenson ” screen, with their bulbs 
four feet above the ground over grass. They consist of a dry-bulb, 
a wet-bulb, a “Rutherford” minimum, and a “Negretti” maxi¬ 
mum. The readings are corrected for index errors, which are very 
slight, being usually nil, and in only one case reaching 0 o, 3. 
The rain-gauge is of the “Snowdon” pattern,*' five inches in 
diameter, and with the rim one foot above the ground, and there¬ 
fore 224 feet above sea-level. The exposure is perfectly open. 
The wind-vane, which rotates freely with the slightest breeze, 
is about 25 feet above the ground, 4 feet above ridge of roof of 
stable, and 105 feet distant from nearest object of equal height. 
All the observations are taken at 9 a.m. and are entered to the 
same day, except the readings of the maximum thermometer and 
the rain-gauge, which are entered to the previous day. The 
adopted mean temperature is the arithmetical mean of the dry- 
bulb (9 a.m.), minimum, and maximum thermometers. The column 
in the principal table headed “ dryness ” expresses the difference 
between the temperature of the air and that of the dew-point. 
Ho secular corrections are applied to any of the readings. 
The following table gives the means of some of the principal 
results of observations taken during the five years 1878-82, for 
each month and for the year:— 
Means of Meteorological Observations taken at Wansford 
House, Watford, 1878-82. 
Months. 
Pressure. 
Temperature. 
Tension 
of 
Vapour. 
Humi¬ 
dity. 
Rainfall. 
Cloud 
0-10. 
Mean. 
Daily 
Range. 
Total. 
Days. 
ins. 
O 
in. 
°/o 
ins. 
January. 
30-177 
34-1 
9*7 
•174 
88 
1-72 
12 
7-5 
February 
29-949 
39’3 
10-4 
•212 
89 
2‘95 
18 
8 -o 
March ..... 
30-024 
42-5 
15-6 
’ 2I 7 
81 
1-46 
13 
6-2 
April. 
29-850 
46*0 
16-2 
•245 
78 
2-77 
16 
6"o 
May .. 
3°' OI 3 
52-8 
i8-3 
•300 
72 
2’34 
14 
6 -i 
June . 
29-918 
57-9 
i6‘2 
•372 
75 
3'94 
19 
7-2 
July . 
29-927 
61 -i 
16-4 
•407 
75 
2-83 
17 
6-6 
August . 
29-883 
6 o -6 
14-2 
'425 
80 
3-66 
15 
7-4 
September 
29-967 
56-8 
16-2 
•389 
84 
2-83 
13 
6-4 
October. 
29-932 
47-6 
131 
•291 
88 
3-5o 
17 
6-6 
November 
29-931 
41*5 
117 
•229 
87 
2-69 
16 
6‘2 
December 
29-927 
36-2 
io ’6 
-194 
9i 
277 
16 
7-2 
Year . 
29-958 
48-0 
14-0 
•288 
82 
33'46 
186 
6-8 
* A “Howard” rain-gauge is used as a check upon the readings of the 
“ Snowdon ” taken when 1 am absent from home. 
