n the top, rear, front, and bottom of the
chair calorimeter.

By following the wiring diagram of the point V, it will be seen that
this will include the connections with the thermal junctions connected
in series and thus give a sum total of the electromotive forces in the
thermal junctions. The point VI is connected with the thermal-junction
system in the air system, indicating the differences in temperature
between the ingoing and outgoing air. It will be noted that there are
four sections in the chair calorimeter, while in the bed calorimeter
there are but three, and hence a special switch S_{3} is installed to
insure proper connections when the bed calorimeter is in use.

This system of connecting the thermal junctions in different sections to
the galvanometer makes possible a more accurate control of the
temperatures in the various parts, and while the algebraic sum of the
temperature differences of the parts may equal zero, it is conceivable
that there may be a condition in the calorimeter when there is a
considerable amount of heat passing out through the top, for example,
compensated exactly by the heat which passes in at the bottom, and while
with the top section there would be a large plus deflection on the
galvanometer, thus indicating that the air around the zinc wall was too
cold and that heat was passing out, there would be a corresponding minus
deflection on the bottom section, indicating the reverse conditions. The
two may exactly balance each other, but it has been found advantageous
to consider each section as a unit by itself and to attempt delicate
temperature control of each individual unit. This has been made possible
by the electrical connections, as shown on the diagram.

RHEOSTAT FOR HEATING.

The rheostat for heating the air-spaces and the returning air-current
about the zinc wall is placed on the observer's table and is indicated
in the diagram as R_{2}. There are five different sets of
contact-points, marked 1, 2, 3, 4, and 5. One end of the rheostat is
connected directly with the 110-volt circuit through the main switch
S_{5}. The other side of the switch S_{5} connects directly with the
point on the middle of switch S_{10}, and when this middle point is
joined with either _f_ and F, direct connection is insured between all
the various heating-circuits on the calorimeter in use. The various
numbered points on the rheostat R_{2}, are connected with the binding
posts on S_{10}, and each c