orward, raises T' by means of a roller bearing U, and when the handle
is raised the total weight of the cylinders is supported on the
platforms.

The balance is attached to an upright I-beam which is anchored to the
floor and ceiling of the calorimeter laboratory. Two large turnbuckle
eye-bolts give still greater rigidity at the bottom. The whole apparatus
is inclosed in a glass case, shown in fig. 5.

AUTOMATIC CONTROL OF OXYGEN SUPPLY.

The use of the reduction-valve has made the automatic control of the
oxygen supply much simpler than in the apparatus formerly used. The
details of the connections somewhat schematically outlined are given in
fig. 32, in which D is the oxygen cylinder, K the supporting band, A the
reduction-valve, and J the tension-equalizer attached to one of the
calorimeters. Having reduced the pressure to about 2 pounds by means of
the reduction-valve, the supply of oxygen can be shut off by putting a
pinch-cock on a rubber pipe leading from the reduction-valve to the
calorimeters. Instead of using the ordinary screw pinch-cock, this
connection is closed by a spring clamp. The spring E draws on the rod
which is connected at L and pinches the rubber tube tightly. The tension
at E can be released by an electro-magnet F, which when magnetized
exercises a pull on the iron rod, extends the spring E, and
simultaneously releases the pressure on the rubber tube at L. To make
the control perfectly automatic, the apparatus shown on the top of the
tension-equalizer J is employed. A wire ring, with a wire support, is
caused to pass up through a bearing fastened to the clamp above J. As
the air inside of the whole system becomes diminished in volume and the
rubber cap J sinks, there is a point at which a metal loop dips into two
mercury cups C and C', thus closing the circuit, which causes a current
of electricity to pass through F. This releases the pressure at L,
oxygen rushes in, and the rubber bag J becomes distended. As it is
distended, it lifts the metal loop out of the cups, C and C', and the
circuit is broken. There is, therefore, an alternate opening and closing
of this circuit with a corresponding admission of oxygen. The exact
position of the rubber diaphragm can be read when desired from a pointer
on a graduated scale attached to a support holding the terminals of the
electric wires. More frequently, however, when the volume is required,
instead of filling the bag to a definite point, as shown by