FROM SELECTED DAYS DURING THE SEVEN YEARS 1898 TO 1904. 321 
important to ascertain what this difference really amounted to. Fortunately, Kew is 
a first order meteorological station, so that exceptionally full information is available 
as to the hourly and the mean daily and monthly values of the meteorological 
elements. 
A comparison was accordingly instituted between mean values deduced for each 
month from the 10 selected days and the corresponding published means taken from 
all days of the month. This was done for the mean barometric pressure of the day, 
the mean temperature, the mean hourly wind velocity, and the daily record of bright 
sunshine. All these elements are recorded directly by self-recording instruments of 
high accuracy, and the pressure and temperature daily means are based on hourly 
readings. The means from all days of the month are regularly calculated and 
recorded by the Meteorological Office; the means from the selected days were 
specially calculated by members of the Observatory staff. 
The results of the comparison appear in Table XI. 
It is at once apparent that the 10 selected days represent a climate having more 
sunshine and a higher barometer than Kew, but which has a distinctly lower winter 
temperature, and in most months of the year appreciably less wind. In summer the 
temperature of the selected days is, if anything, slightly above the normal, but the 
difference is too small to rely on. Absolutely considered, the difference as regards 
sunshine is largest in summer; but relative to the average amount actually 
experienced the difference is really greater in winter. 
1 able XI. Mean Excess of Element on the 10 Selected Days as compared to All 
Days of the Month. 
Barometric 
pressure (inches). 
Temperature, 
Fahrenheit. 
Wind run, miles 
per hour. 
Sunshine, hours 
per day. 
January .... 
. . +0-132 
0 
-2-98 
- 1-98 
+ 1 - 02 
February. . . . 
. . - 0-001 
- 1-70 
-2-28 
+ 0-33 
March .... 
+ 0-083 
-0-98 
- 1-93 
+ 0-38 
April . 
. . +0-090 
-0-79 
-1-30 
+ 1-75 
May . 
+ 0-096 
-0-14 
- 1-09 
+ 1-79 
June . 
. . +0-068 
+ 0-17 
-0-09 
+ 1-40 
July . 
. . + 0-010 
+ 0-50 
+ 0-12 
+ 0-96 
August .... 
. . +0-055 
- 0-01 
-0-48 
+ 1-36 
September . . . 
. . +0-017 
+ 0-40 
-0-78 
+ 1-13 
October .... 
+ 0-042 
- 1-12 
+ 0-79 
+ 0-95 
November . 
. . + 0-101 
-2-35 
-0-91 
+ 0-12 
December . . . 
. . + 0-101 
-3-08 
- 3-21 
+ 0-02 
Year .... 
- 1-01 
- 1-10 
+ 0-93 
Winter .... 
-2-53 
- 2-10 
+ 0-37 
Equinox .... 
. . +0-058 
-0-62 
-0-80 
+ 1-05 
Summer . 
. . ; +0-057 
1 
+ 0-13 
- 0-39 
+ 1-38 
2 T 
VOL. ccvi.—A. 
