(1) the area of brine
coils can be increased or decreased by using one, two, or all three of
the coils; or (2) the amount of air passing over the cooling pipes may
be varied by changing the speed of the blower. In practice substantially
all of the regulation is effected by varying the position of the
controlling lever on the regulating rheostat. The apparatus functionates
perfectly and the calorimeter room can be held at 20 deg. C. day in and
day out, whether the temperature outdoors is 40 deg. below or 100 deg.
above 0 deg. F.

It can be seen, also, that this system provides a very satisfactory
regulation of the humidity, for as the air passes over the brine coils
the moisture is in large part frozen out. As yet, no hygrometric study
has been made of the air conditions over a long period, but the
apparatus is sufficiently efficient to insure thorough electrical
insulation and absence of leakage in the intricate electrical
connections on the calorimeters.

The calorimeters employ the thermo-electric element with its low
potential and a D'Arsonval galvanometer of high sensibility, and in
close proximity it is necessary to use the 110-volt current for heating,
consequently the highest degree of insulation is necessary to prevent
disturbing leakage of current.

The respiration calorimeter laboratory is so large, the number of
assistants in the room at any time is (relatively speaking) so small,
seldom exceeding ten, and the humidity and temperature are so very
thoroughly controlled, that as yet it has been entirely unnecessary to
utilize even the relatively small amount of indirect ventilation
provided in the original plans.

During the greater part of the winter it is necessary to use only one of
the thermostats and the radiators connected with the other can be shut
off, since each radiator can be independently closed by the valves on
the steam supply and return which go through the floor to the basement.
The temperature control of this room is therefore very satisfactory and
economical.

It is not necessary here to go into the advantages of temperature
control of the working rooms during the summer months. Every one seems
to be thoroughly convinced that it is necessary to heat rooms in the
winter, but our experience thus far has shown that it is no less
important to cool the laboratory and control the temperature and
moisture during the summer months, as by this means both the efficiency
and endurance of the assi