310 (Feb. I, 
Briggs. | 
Airat commence- Change during Air at end ofone 
ment, cu. ft. hour, cu. ft. hour, cu. ft. 
O 157.53 — 4.91 152.62 
N 630.13 eine 630.138 
CO, @ 4 to 10,000 0.32 ae ED) 2.74 
H,O Ibs. 0.56 12.02 + 5.42 (0.253 lbs.) 17.44 
800. 
Gas 4. 
804. 803.03 
Temperature 70° = 174.2° (2488 units) 244.2° !!! 
The figures for reduction of the 2488 units are as follows: 800 cubic 
feet of air at 0.075 lbs. per foot (weight at 70°) = 60 1bs. multipled by specific 
heat of air, 0.238 = 14.28 and 2488 = 174.2.° This result might be amended 
by computation of the relation of the pressure and temperature for the 
supposed constant volume of air in the room, but it is too preposterous to 
need further estimate. 
It might be argued that the condition of a closed, perfect heat-retaining 
room is not asupposable one, and I will proceed to compare the effect of this 
quantity of heat in similar room where the loss of heat is an ascertainable 
quantity, taking the same room of 800 cubic feet capacity. Such a room, with 
an outer wall exposure of not over one-sixth its enclosing surface (the one 
side of a cube), which outer wall has the usual proportion of window surface 
and presents a mean aspect to the points of the compass (W. or E. about), 
will be heated by currents of air coming from steam heated surfaces when 
one foot of surface is provided for each 80 cubic feet of contents. A temp- 
erature of 70° will be maintained within the room against an out-door 
temperature of zero with this ratio of surface. 
In performance of this warming the steam surface of ten square feet may 
derive its air from out of doors at zero, and there will be furnished in the 
room three cubic feet of air at the temperature of 100° (heated from zero) 
each minute for each square foot of steam surface, or 30 cubic feet of air in 
all, heated at 100,° will supply heat for this room. The room is taken at 
70°, and consequently 30° of the heated air will have been expended each 
minute in heating it, or 900 air feet units—900 x 0.238 x 0.075 = 16 units 
of heat per minute x 60 = 960 units per hour. These figures are gross 
approximations of actual heat effects of steam heated surfaces, or of capacity 
to heat a room against losses from the walls, etc., but they are practical in 
representing what is sure to be accomplished in house warming and ven- 
tilation, and they exhibit conclusively that, unless some other laws of heat 
from gas lights exist than those which radiate or communicate to the air 
by convection, we must look for a considerable reduction in the heat-pro- 
ducing effect from what is deduced from rigorous application of the estab- 
lished laws of heat of combustion. It is certain that a four foot burner 
does not give out nearly three times as much heat as will heat a small 
room on the coldest day of winter. 
