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 actuates a revolution counter, and a clock measures the time employed in the experiment.  In order to obtain a simultaneous starting and stopping point for all these apparatus, they are connected electrically, and, through the maneuver of a commutator, are all controlled at once.  The electric current is furnished by two series of bichromate batteries.

The tests of traction machines are effected by means of a three-wheeled vehicle carrying a dynamometer.  The front wheel is capable of turning freely in the horizontal plane, and the dynamometer is mounted upon a frame provided with a screw that permits of regulating its position according to the slope of the ground.  The method of suspension of the dynamometer allows it to take automatically the inclination of the line of traction without any torsion of the plates.  There are two models of this vehicle, one designed to be drawn by a man, and the other by a horse.