ation the work will be equally constant, but care
will be taken always to have a sufficient reserve. Electric lighting
will form a considerable part of the duty to be done from this
station, and in all cases it is intended to work with accumulators, so
that the resistance to be overcome by the engines, so far as this part
of the duty is concerned, will be well known and uniform. The
engineers of the Compressed Air Co., of Paris, have during the last
five years acquired an experience which could only be attained at a
high price and at the expense of a certain amount of failure; this
period, it is claimed, is now passed, and in the new installation it
is possible to put into practice all the valuable lessons learned at
St. Fargeau, to say nothing of the more favorable natural conditions
under which the extension is being started and the improvements in the
compression of the air made by Mr. Popp and Professor Riedler, and to
which we shall refer later.

Chiefly in consequence of the high value of the ground, vertical
engines were adopted at the new station; the proximity to the river
made the foundations somewhat costly, and the risk of occasional
floods rendered it desirable to set the level of the engine bedplates
20 inches above the floor of the building; the foundations of the
engines are continuous, but are quite independent of the building.
There are three compressing cylinders in each set of engines, one
being above each steam cylinder. Two of these are employed to compress
the air to about 30 lb. per square inch, after which it passes into a
receiver and is cooled; it is then admitted into the third or final
compressing cylinder and raised to the working pressure at which it
flows into the mains. In the illustrations, h, m, and b are the high,
intermediate, and low pressure cylinders of one set of engines; as
will be seen, each cylinder is on a separate frame connected by
girders; directly above the cylinders are the two low and the one high
pressure air cylinders, b