12‘2 
MR. GLAISHER ON THE RADIATION OF HEAT, 
standard. Among others received in January 1843, were five of the form finally 
adopted for use, and the following are the comparisons with the standard, made by 
hanging them in the air and near to the latter : — 
1843. 
Month, day, 
and hour. 
Reading of 
standard 
thermometer. 
Reading of thermometers. 
a . 
b. 
C. 
d. 
e. 
d. h. 
o 
O 
o 
Feb. 5 22 
34-8 
34-8 
34-8 
34-8 
34-8 
34-7 
6 0 
35-7 
35-4 
35*6 
35-6 
35-6 
35-7 
6 1 
36-4 
36-2 
36*3 
36-2 
36-3 
36-3 
13 22 
35*9 
35-8 
36-0 
35-8 
35-9 
35-9 
13 22\ 
36-4 
35-9 
36-0 
36-1 
36*2 
36-3 
13 23 
37-0 
36-8 
37*0 
37-0 
37-0 
37-4 
14 1 
39-0 
38-8 
39-0 
39-2 
39-2 
39-2 
The following comparisons were made of those received on September 13th by 
means of water of different temperatures in the following manner. Water of a higher 
temperature than needed was placed in a vessel, and the required temperature was 
obtained by the application of cold water, the two being well mixed together till the 
standard thermometer read the same at every part of the mixture. The thermo- 
meters were then all placed in it and parallel to each other ; they were thus allowed to 
remain for one hour, and their readings were taken quickly. Water of a different 
temperature was then prepared in a similar way, and so on successively. The com- 
parisons occupied an entire night, and during this interval of time the temperature 
of the room was kept uniform, in fact it did not vary one degree. 
This method was found to be very troublesome, and to ensure accuracy a 
long time was required to be devoted to it. The mixing of water of different 
temperatures together, so that the whole mixture became of the same temperature, 
from the circumstance of its being so bad a conductor of heat, was found to be 
difficult. After this time I adopted the following method in all subsequent compa- 
risons : — 
1st. The water was heated to a temperature above the highest required. 
2nd. The standard and all the thermometers for comparison were placed, in this 
water, parallel to each other, and after some time their readings were taken as 
quickly as possible. 
3rd. The readings were afterwards taken as the temperature of the water declined 
every 2° or 3°, till the temperature of the water was at or near that of the apartment ; 
in case the decline of temperature was found to be too rapid, the surface of the water 
was covered by flannel. 
4th. A quantity of water was cooled to a point lower than the lowest required 
temperature, by means of ice, or of ice and salt, and the thermometers were placed 
in this as before. 
5th. The readings of all the thermometers were taken as this mixture increased 
2° or 3 C in temperature, till it was at or near the temperature of the apartment, its 
surface being covered by flannel if the increase of heat was thought to be too rapid. 
