2G STORRS AGRICULTURAL EXPERIMENT STATION. 
measurements are so delicate that even slight movements of the person inside, 
such as rising froin the chair, reveal themselves to the observer outside by the 
immediate rise in the thermometric reading. 
Regulation of temperature of ingoing air.—In order that the ventilating cur- 
rent of air shall not carry out of the chamber any more or any less heat than it 
brings in, the temperature must be the same when it enters as when it leaves. 
Accordingly the incoming air, which leaves the brine tank at a very low tem- 
perature, is warmed, before its entrance to the chamber, to the temperature of 
the outgoing air. The devices for this purpose are such that the difference of 
temperature of the incoming and outgoing currents can be kept inside of .o1 
degree C. In actual experiments the positive and negative differences are made 
to counterbalance each other. | 
Arrangements for preventing the passage of heat through the walls of the 
calorimeter.—The difference between the temperature of the copper wall and 
that of the zinc is measured by a system of thermo-electric junctions, in 304 
pairs, distributed over the sides, top and bottom, one-half of the junctions (iron- 
German silver) being in close thermal contact with the copper wall and the other 
half, (German silver-iron) with the zinc wali. The difference of temperature 
of the two walls is made as small as possible by warming or cooling the air 
in the space B, and the positive and negative differences are made to counter- 
balance each other. Thus the corresponding movements of small quantities of 
heat inward and outward also counterbalance, and the chamber neither gains 
nor loses heat through the walls. 
For the measurement of differences of temperature, as well as for the warming 
and cooling, the walls of the calorimeter are considered as divided into four 
sections, viz.:—(1) the top; (2) the upper half of the sides or ‘‘upper zone”; 
(3) the lower half of the sides or ‘‘ lower zone ”s (4) the bottom. The systems 
of thermo-electric elements for heat measurements, of wires for warming and of 
water pipes for cooling, are each divided into corresponding sections. 
The observer's table.—This is shown in figure g at the left, in front of the . 
brick pier. A shelf fastened to the pier and shown on the tight of the latter, 
behind the table in the picture, holds the galvanometer and scale. The scale is 
seen in the picture at the front end of the shelf over the table. The galvan- 
ometer is at the other end of the shelf, two meters from the scale and obscured 
by the pier. On the table are the switches to bring the various circuits into 
connection with the galvanometer, and with them the Wheatstone bridges, and 
the banks of electric lamps for varying the heating currents. At the front of the 
table near the chair is the record book for noting the observations, which are 
very numerous. Plans are being made to move the table to the end of the 
chamber near the door. 
With the aid of the devices thus briefly described an experienced operator at 
the observer’s table can easily control the temperature of B and make it follow 
the variations of the interior of the chamber very closely. When the rate of 
generation of the heat in the chamber is reasonably uniform and the temperature 
is nearly constant, the deflection of the image on the scale at the observer's 
table can usually be kept within one division of the scale, which means an 
average difference of temperature between the copper and zinc walls of less than 




