THE ROYAL SOCIETY, AND AT THE ROYAL OBSERVATORY, GREENWICH. 577 
the water, exceeds that at the observatory at 6 a.m. by 1°'6 ; i°’0 ; 0"‘8 ; 0°‘3 ; 0°'6 ; 0°'7; 
0°'9 ; 0’°8 ; 0°’2 ; 0°'0 and 0°*8, in the twelve months respectively ; and at 6 p.m. by 1°‘2 ; 
0°‘8 ; 1°‘0 ; 0°'8 ; 0°'7 ; 0°*8; 0°‘6 ; 0°‘8; 1°‘3 ; l°-0 ; 1°'7 and 0°‘9, in the twelve months 
respectively ; that at 9 a.m. it was in excess in January by 1°‘3 ; February by 1°'5 ; 
March by 0°’6 ; April by 0®4 ; May by 2°-2 ; June by 0°'4 ; and in October by 0°5 ; 
that it was of a lower temperature in July by 0°‘7 ; August by 0°'5 ; and in September 
by 0°'l ; that at 9 p.m. it was always of a higher temperature : the excesses were 0°'l ; 
0°‘3 ; 0°7 ; 0°‘3 ; 1°‘9; 2°-9 ; 1°*5 ; 3°‘2 ; 1°‘2 and l°-3 respectively. 
From these numbers, it seems that during the night hours, at all seasons of the 
year, the temperature of the air at the Dreadnought Hospital Ship is higher than at 
the Observatory, and that it is below only during the midday hours. 
At times of extreme temperature the effect of the water upon the temperature of 
the air is very great. On February 12, 1847, the temperature of the air at my house, 
which is situated about one mile and a half from the river, was 6°‘0 ; the lowest 
reading, 32 feet above the water of the Thames, was 16°'0; the temperature of the 
water was 33° ; its heating effect upon the air in its immediate vicinity amounted to 
10°; at the Observatory the reading was 10°‘5; and the heat of the water of the 
Thames seems to have influenced the temperature of the air at the Observatory to 
the amount of 4°. Some time since, on comparing the temperatures of the air as 
recorded in the Philosophical Transactions in the year 1814, with corresponding tem- 
peratures as observed at Greenwich, I doubted the accuracy of the former in many 
instances, on account of their much higher values; these investigations have now led 
me to believe that the temperatures, as recorded in the Philosophical Transactions for 
that year, are correct. 
Table XIV. — Comparison of the mean temperature of the Air at St. John’s Wood, 
and at the Royal Observatory, Greenwich. 
Month. 
1841. 
1842. 
1843, 
Mean temperature of the air. 
Mean temperature of the air. 
Mean temperature of the air. 
At 
Royal Ob- 
servatory, 
Greenwich. 
At 
St. John’s 
Wood. 
In 
excess at 
St. John’s 
Wood. 
At 
Royal Ob- 
servatory, 
Greenwich. 
At 
St. John’s 
Wood. 
In 
excess at 
St. John’s 
Wood. 
At 
Royal Ob- 
servatory, 
Greenwich. 
At 
St. John’s 
Wood. 
In 
excess at 
St. John’s 
Wood. 
January 
33-6 
34-3 
+ 0*7 
32-9 
32-4 
O 
- 0-5 
39-9 
39-1 
O 
— 0-8 
February ... 
35-3 
36*5 
+ 1-2 
40-8 
40-3 
- 0-5 
36*0 
36-1 
-l-O-l 
March 
46-2 
46-6 
- 1 - 0-4 
44-9 
44-3 
- 0-6 
42-9 
42-9 
0-0 
April 
47-0 
46-6 
- 0-4 
45-2 
46-3 
+ M 
47-1 
47-6 
+ 0-5 
May 
56-8 
57-0 
+ 0-2 
53-2 
53-2 
0-0 
52*2 
51-2 
— 1-0 
June 
56-4 
55-9 
- 0-5 
62*9 
62-5 
- 0-4 
56*3 
55*2 
— 1-1 
July 
57-8 
56*9 
- 0-9 
60-2 
59-3 
- 0*7 
60-9 
60-1 
- 0-8 
August 
60*5 
59-5 
— 1-0 
65‘4 
65-5 
-fO-I 
62-1 
61-9 
— 0-2 
September ... 
58-5 
57-8 
- 0*7 
56-4 
56-2 
— 0-2 
59-5 
60*3 
- hO-8 
October 
48-8 
49-1 
-f 0-3 
45-4 
45-8 
- t - 0-4 
48-0 
47-6 
- 0-4 
November ... 
42-7 
42-5 
— 0-2 
42-8 
43-3 
-f 0-5 
43-8 
43-9 
+ 0-1 
December ... 
40-5 
40-2 
- 0-3 
45-0 
44-6 
- 0-4 
43-9 
44-2 
+ 0-3 
4 E 
MDCCCL . 
