124 THE ROYAL SOCIETY OF CANADA 



able, if one or both of these other factors are sufficiently varied. The 

 equable temperature and comparatively equable humidity in many 

 parts of Britain, have prevented industrial humidity problems from 

 appearing there in such a way that the difficulties elsewhere could be 

 fully appreciated. In endeavouring to duplicate the British condi- 

 tions under circumstances where for example the inside and outside 

 temperatures may sometimes differ by more than 90°F., manu- 

 facturers have repeatedly acted on advice which is incomplete, and 

 have, as a consequence, sometimes been entirely unable to obtain a 

 product of the desired quality. 



There remains one well known contention for the advantageous 

 use of the quantity, relative humidity. Meteorologists and physiolo- 

 gists have generally assumed that it is an essential factor in gauging 

 the comfort of the atmosphere. It has, however, been shown very 

 conclusively by Hill,^ J. R. Milne^ and others,^ that the quantity, 

 relative humidity, is very misleading in these records, and that its use 

 has led to several contentions since shown to be mistaken. 



Within certain limits the temperature of the air, the relative 

 humidity and the velocity of movement of the air, may all vary in such 

 a manner that our sense of comfort remains unchanged, but on the 

 other hand our sense of comfort may alter appreciably without any 

 change in either temperature or relative humidity. It is as necessary 

 to consider the circulation of the air as it is the humidity or the tem- 

 perature, and Hill suggests the adoption of the rate of heat loss of a 

 wet bulb at body temperatures, as an inclusive quantity which em- 

 braces these factors, and provides a direct means of comparing com- 

 fort conditions. By the use of the kata-thermometer this factor can 

 readily be obtained, and it has been found to indicate the conditions 

 of comfort much more satisfactorily than by consideration of tem- 

 perature and humidity alone. Further, the condition of comfort is 

 indicated by the one inclusive factor instead of by two or more with 

 conflicting variations, and if desired, there can be obtained by means 

 of formulae and tables very approximate values for temperature, 

 vapour pressure, and velocity of air movement, as well as for relative 

 humidity, dew-point and rate of evaporation. 



A series of observations on the atmospheric conditions for com- 

 fort both indoors and outdoors, during the winter and spring months, 

 has been carried out at Macdonald College, Ste. Anne de Bellevue, 



iHill, Griffith and Flack, loc. cit.; also Hill, Nature, Vol. 95, p. 205 (April 22nd, 

 1915). 



»J. R. Milne, Jour. Scot. Meteor. Soc, Vol. 16 No. 29, pp. 9-17 (1912) ; also Nature, 

 Vol. 75, p. 260 (May 6, 1915). 



^For example see Reports of N.Y. State Commission on Ventilation. 



