rist may employ to facilitate his
exploitation. However, the tests that are oftenest made are (1) of
rotary apparatus, such as mills, thrashing machines, etc.; (2) of
traction machines, such as wagons, carts, plows, etc.; and (3) of
lifting apparatus. It is possible, also, to make experiments on the
resistance of materials.

The experimental hall contains a 7 horse power gas motor, dynamometers
with automatic registering apparatus, counters, balances, etc. A small
machine shop contains a lathe, a forge, a drilling machine, etc. The
main shaft is 12 meters in length and is 7 centimeters in diameter. It
is supported at a distance of one meter from the floor by four pillow
blocks, and is formed of three sections united by movable coupling
boxes. Out of these 12 meters, 9 are in the hall and 3 extend beyond
the hall to an annex, 14 meters in length and 4 in width, in which
tests are made of machines whose operation creates dust. When the
machines to be tested require more than the power of seven horses that
the motor gives, the persons interested furnish a movable engine,
which, placed under the annex, actuates the driving shaft. Alongside
of the main building there is a ring for experimenting upon machines
actuated by a horse whim. There will soon be erected in the center of
the grounds an 18 meter tower for experiments on pumps. Platforms
spaced 5 meters apart, a crane at the top, and some gauging apparatus
will complete this hydraulic installation.

The equipment of the hall is very complete, and is fitted for all
kinds of experiments.

[Illustration: STATION FOR TESTING AGRICULTURAL MACHINES--DYNAMOMETER
FOR TESTING ROTARY MACHINES.]

The tests of rotary machines are made by means of a dynamometer (see
figure). Two fast pulleys and one loose pulley are interposed between
the machine to be tested and the motor. The pulley connected with the
motor carries along the one connected with the machine, through the
intermedium of spring plates, whose strength varies with the nature of
the apparatus to be tested. The greater or less elongation of these
plates gives the tangential stress exerted by the driving pulley to
carry along the pulley that actuates the machine to be tested. This
elongation is registered by means of a pencil connected with the
spring plates, and which draws a diagram upon a sheet of paper. At the
same time, a special totalizer gives the stress in kilogrammeters.
Besides, the pulley shaft