With the machine can be found average dates, as, for instance, of
purchases and of payments extending over irregular periods; also average
prices, as for "futures," in comman use among cotton brokers. The
problem of average haul, so often presented to the engineer, can be
solved with ease and great celerity. Practical examples of the solution
of these and a number of other problems involving proportions or
averages were given by the author.

* * * * *




COMPOUND BEAM ENGINE.


The engine represented in Figs. 1 to 4 herewith is intended for a mill,
and is of 530 to 800 indicated horse-power, the pressure being seven
atmospheres, and the number of revolutions forty-five per minute. As
will be seen by the drawing each cylinder is placed in a separate
foundation plate, the two connecting rods acting upon cranks keyed
at right angles upon the shaft, W, which carries the drum, T. The
high-pressure cylinder, C, is 760 mm diameter, the low pressure cylinder
being 1,220 mm. diameter, and the piston speed 2.28 m. The drum, which
also fulfills the purpose of a fly wheel, is provided with twenty-eight
grooves for ropes of 50 mm. diameter. With the exception of the
cylinders, pistons, valves, and valve chests, the engines are of the
same size, corresponding to the equal maximum pressures which come into
action in each cylinder, and in this respect alone the engine differs in