1878.] 
Moisture in Air. 
*95 
V. ON THE RELATION OF MOISTURE IN AIR 
TO HEALTH AND COMFORT * 
By Robt. Briggs, C.E., 
Cor. Mem. Am. Inst, of Architects, &c. 
T may be accepted that the most pleasant condition of 
the air, in our portion of the globe, will be found to 
exist on a fair day in early summer, when the temper- 
ature ranges from 62° to 68° F., and the moisture present in 
the air is from 85 to 80 per cent of saturation. On a day 
like this no thought of the weather is taken, and the passage 
of the conversational compliment of a “ fine day ” becomes 
a needless reminder, to be accepted without discussion or 
thought. Admitting this proposition as a faCt, it is the pur- 
pose of this paper to show that in our climate this summer 
condition of relative heat and moisture is not desirable, or 
even attainable, at other seasons, in the ventilating or heating 
of occupied places. And in presenting this view to the 
American Society of Architects I do so with a full knowledge 
that it does not accord with the opinion of most American 
writers on the subject of ventilation, who have derived their 
information and their arguments mainly from the study of 
English and French books, and have only endeavoured to 
reconcile the data found in these to American wants and 
practice. Even Wyman, who is by far the most original as 
an observer, as well as the most thorough as the collator of 
information from all sources, hardly makes the distinctive 
effeCt of our low temperature, combined with a comparatively 
lower dew-point, sufficiently evident. 
Except one investigates the relation of moisture to tem- 
perature of air in the two countries, it is impossible to 
reconcile our faCts with the statement of good foreign 
authorities, t that 56° is comfortable, and 62° is warm, in 
* Paper read before the Am. Institute of Architects, at Boston, Oct. 18th, 
1877. From the Journal of the Franklin Institute. 
f The comfortable warmth of air indoors is given by various authorities, as 
follows : — Peclet, Traite de la la Chaleur, gives 15 0 C., 59° F. Morin, 
Etudes sur la Ventilation, — for nurseries, schools, &c., 59°; hospitals, 6i° to 
64°; theatres, assembly halls, &c., 66° to 68° ! Tredgold, Principles of 
Warming and Ventilating, &c., 56° to 62°. Reed, Illustrations of the Theory 
and Practice of Ventilation, 65°. Hood, Treatise on Warming Buildings, &c., 
inferentially 55 0 to 58°. Parkes, Manual of Military Hygiene, 48 s to 70° (this 
author has encountered the difficulty of naming a fixed temperature, and 
avoids the issue). Box, Practical Treatise on Heat, 62°. Others might be 
quoted, but these are amongst the best authorities on Heating and Ventilation. 
O 2 
