92 THE ROYAL SOCIETY OF CANADA 
it should not be adopted as the chief means of defining the condition 
of humidity unless some especial advantage is gained thereby. Such 
an advantage may be claimed on the ground that the dryness or 
dampness of the air is of prime interest in this connection to meteor- 
ologists and physiologists, but this should not however, be the case. 
It has recently been pointed out very clearly by Dr. Leonard Hill, 
F.R.S.,! that the relative humidity is not the chief atmospheric 
factor on which our “‘sense of comfort” depends. Within certain 
limits the temperature of the air, the vapour pressure and the velocity 
of movement of the air may all vary in such a way that our ‘‘sense 
of comfort’? remains unchanged, and on the other hand ‘our sense 
of comfort” may vary without a change in the relative humidity. 
Dr. Hill shows that the rate of heat-loss at body temperatures is an 
inclusive quantity which does provide a direct means of guaging 
our sense of comfort. 
In chemical and physical problems it is usually either the moisture 
content or the aqueous vapour pressure of a sample of gas which is 
of more interest than its relative humidity. It is suggested, therefore, 
that it would be more convenient if humidity records contained the 
existing vapour pressure (or the absolute humidity) and the temper- 
ature rather than the relative humidity anc the temperature. 
The application of the hygrometer outlined in section 3 as a 
“wet kata-thermometer’? for a direct determination of the “sense 
of comfort” factor, measuring the rate of heat-loss in milli-calories 
per sq. cm. per sec., should be advantageous. If the electrical method 
could be perfected, it would probably be avilable for the determination 
of this quantity without appreciable modification. 
Many thanks are due to Dr. C. J. Lynde for his kind interest 
in the present investigation. 
Macdonald College, 
McGill University. 
May, 1916. 


1 Hill, Griffith and Flack, Phil. Trans. Rey. Soc. Lon., Series B, Vol. 207, pp. 
183-220. 
2 Hill, Griffith and Flack. Loc. cit. 
