294 ILLINOIS ACADEMY OF SCIENCE 
possible, of the volatile matter, then a free-burning, easily dis- 
tilled coal should be used. If the conditions are such that the 
fire must be controlled chiefly by preventing the combustion of 
the volatile matter then the less easily distilled coal, the slow 
burning coal, should be used. 
4. When used for domestic purposes coal is usually used: 
First, for house heating; second, for laundry purposes; third, 
for cooking. If the foregoing conclusions are justified, gen- 
erally speaking, a slow-burning coal is most suitable for house 
heating; a free-burning coal is most suitable for laundry pur- 
poses; and, depending upon conditions, either a free-burning 
or a slow-burning coal may be found most suitable for cooking 
purposes. 
5. I believe that extensive study of the rate at which bi- 
tuminous coals burn under ordinary conditions for domestic 
use would be of great value to the people of Illinois. 
INDOOR HUMIDITY 
Frep D. BARBER, ILLINOIS STATE NORMAL UNIVERSITY 
Much has been written in recent years about the low indoor 
humidity prevalent throughout the winter months when arti- 
ficial heat ‘s required. The evil effects of low indoor humidity 
(and the consequent rapid evaporation from every moist sur- 
face) upon health have frequently been discussed. Much has 
been said in commendation of a dry climate, such as that of 
the southwestern United States, with moderate winter tem- 
peratures enabling the residents to live practically out of doors 
the year around; little has been said in favor of the winter 
climate of northeastern United States. The change from the 
outdoor air with its low temperature and high humidity, to 
the indoor air with its high temperature and low humidity, or 
vice versa, is generally conceded to be a trying ordeal. Many 
suggestions have been offered for controlling the humidity of 
residences, school-rooms and public halls. In some instances 
efforts in this direction have been more or less successful; it 
is to be feared that in most cases they have been less successful. 
