124 THE ANTARCTIC MANUAL. 
With the prevalent dilettante character of meteorology its exist- 
ence was forgotten, and its application fell into desuetude. 
The subject is dealt with in great detail and quite exhaustively 
in the works of Newton, Lambert, Leslie, and others. For profound 
but, at the same time, simple treatment of this interesting subject, 
the writings of these great men cannot be surpassed. 
The method of determining the rate or term of cooling of a 
thermometer is simplicity itself; indeed, it can be carried out even 
in a shop, so that we need never buy a thermometer in ignorance of 
what may be termed its thermal nimbleness. 
The necessary observations are best made in a dwelling-room of 
fair size, in which the air remains for at least a considerable time at 
a constant temperature. The thermometer, which is not attached to 
any backing, is whirled in the air until it assumes a constant 
temperature. This is noted as the temperature of the air at the 
time. The thermometer is then hung up in the middle of the room, 
and a reading telescope should be set up at a little distance from it, 
so that its scale can be read without approaching too near. Except 
in particular cases, as for persons who are short-sighted, the telescope 
is not absolutely indispensable. The bulb of the thermometer is then 
warmed in any convenient way, as by the heat of the hand through 
a fine cloth, to prevent soiling the glass. The temperature of the 
thermometer should be raised from fifteen to twenty degrees above 
that of the air. It is then allowed to cool while hanging quite 
motionless in the air. When its temperature has fallen a few 
degrees time is taken to the nearest second when the mercury passes 
a given division. It is then observed as it falls, at regular equal 
intervals of time. The length of these intervals of time is regulated 
by the rapidity with which the thermometer cools, and may con- 
veniently be 5, 10, 20, 30, or even 60 seconds. The observations 
should b2 continued until the temperature of the thermometer has 
fallen to about two degrees above that of the air. This should not 
have changed during the operation. If there has been any sensible 
variation the observations should be rejected, and the operation 
should be repeated when there ig no variation. 
The principle which should find interpretation in the observations 
is that in equal intervals of time the bulb of the thermometer loses equal 
Sractions of the heat which it possessed at the beginning of the rnterval. 
Here heat is understood to mean excess of heat, or the heat corre- 
sponding to temperatures above that of the medium in which the 
thermometer is cooling, 
If time has been taken when the temperature of the thermometer 
