In the new installation 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, b¹, m¹, and h¹ respectively.  The former deliver the air compressed to the first stage into the receiver, T¹ (see Fig. 5), whence it passes into the third compression cylinder, and thence by a main into the cylinders, R R, which are in direct communication with the delivery mains; these mains terminate in the subway, T. The water for condensation is brought into the engine house by the channel, C, and the condenser pumps, a, draw direct from this supply; the discharge main back to the river is shown at A. The relative positions of the engine and boiler houses are indicated in Figs. 2 to 5, where F shows the end of one group of boilers; the air supply for the compressors is led from the central raised portion, S, of the roof.