in the reduced brake pipe; it will be recalled that in response to a 10-pound brake-pipe reduction the pressure built up in the brake cylinder should be about 25 pounds, if the piston travel is correct; but in this arrangement there is no variable-traveling piston that can alter the result of the pressure expansion, and following a 10-pound reduction the application chamber will have 25 pounds pressure; this 25 pounds acting upon application piston 10, in application cylinder G, will force it to the left, unseating valve 5 and permitting main-reservoir air from chamber a to enter chamber b and pass from there to the brake cylinders of the engine and tender; and when-regardless of what distance the pistons may travel in the brake cylinders -their pressures become 25 pounds, or a very little greater, the same pressure being contained in chamber b, there is an equalization of pressure on piston 10, and the spring reacting upon valve 5 closes it and pressure supply to the brake cylinder ceases-until the pressure of chamber b and the brake cylinders begins to reduce through leakage, whereupon the greater pressure in application cylinder G again unseats the application valve, 5, and the brake cylinders are resupplied up to equalization, when the valve is closed as before. This automatic pressure-maintenance will be continuous as long as the charge remains in the application chamber; but when an increase of brake-pipe pressure moves

the equalizing valve to release position, the air in the application chamber is exhausted to the atmosphere in the same manner as was explained in reference to the triple valve; or its discharge may be effected by the independent brake-valve (through a pipe connection not shown in the Fig. 5 diagram); but in either or any case, when the pressure of the application chamber is reduced wholly or in part, an exhaust valve which is not shown automatically releases the pressure from the brake cylinders in conformity to the exhaust of the application-chamber air-pound for pound; such additional functions of the distributing valve will be explained in detail further along, as at this time it is only desired to illustrate the application principle.

THE NO. 6 E-T DISTRIBUTING VALVE.

The distributing valve as a whole, consists of two sections bolted firmly together (see Fig. 6), one of which contains the operating apparatus-valves, pistons, etc.—and may be subdivided into two portions, the lower, or "equalizing portion," which we have already compared to a triple valve, and the upper, or "application portion," that directly controls the flow of pressure from main reservoir to brake cylinders, and from brake cylinders to the atmosphere in releasing the brake (see Fig. 7); the other section is called the "doublechamber reservoir," and it is also divided, as the name implies, by a partition or bulkhead which is part of the main-body casting, and air-tight, into two chambers which are called the "pressure chamber," and the "application chamber" (Fig. 6), and which will be understood as corresponding to an auxiliary reservoir and a dummy brake cylinder, respectively, to furnish the pressure-volumes for the correct operation of the equalizing, or triple valve, portion of the distributing valve; and the application chamber is ordinarily in connection with the application cylinder (in Fig. 7, the space closed by the cylinder head, 7), in which its pressure acts upon application piston 10, in part as described in connection with the diagrammatic Fig. 5.

In the ideal sketch of Fig. 5, the pressure chamber and application chamber were shown in comparatively the same size as the regular auxiliary reservoir and brake cylinder of the automatic-brake system, and it was explained that the ratio of pressure supply to the application chamber and application cylinder conforms to the normal pressures obtained in brake cylinders of the common automatic system; as long as the sizes of an auxiliary reservoir and brake cylinder are proportionately the same their actual sizes may be reduced or increased to any extent without changing the ratio of equalization of pressure between them; and as the sole duty of their E-T counterparts are to furnish pressure to the comparatively small application cylinder, the reservoir containing the pressure chamber and application chamber is made so small as to take up but little room.

Referring to Fig. 7: It should be understood at first that the equalizing portion and pressure chamber are used in automatic applications only, service reductions of brake-pipe pressure causing the equalizing valve to connect the pressure chamber to the application chamber and application cylinder, allowing air to flow from the former to the latter two-to the application chamber, for expansion to the pressure equivalent to that which is desired in the brake cylinders, and to the application cylinder as the actuating power to be applied to the

application side of piston 10 (upper portion). The upper slide valve, 5, connected to the spindle, or stem, of piston 10, holds main-reservoir pressure above it and admits a graduated amount of it to the brake cylinders when the locomotive brake is applied—an amount to correspond to the pressure in the application cylinder—and is called the "application valve,” while the under one, 16, is used to release the pressure from the brake cylinders and is named the "exhaust valve"; in Fig. 7 the space between piston 10 and the head, 7, is the application cylinder, and the whole space to the right of piston 10 as far as cap-nut 22 is in permanent connection with the locomotivebrake cylinders; any greater pressure in the application cylinder than may be in the brake cylinders will, it can be plainly seen, force the application piston, 10, to the right, to close the exhaust valve and open the application valve, admitting main-reservoir air to the brake cylinders until their pressure equals that in the application cylinder; also, any variation of applicationcylinder pressure will be exactly duplicated in the locomotive-brake cylinders, and the resulting pressure maintained regardless of almost any brake-cylinder leakage.

It is obvious that the pressure supply to the brake cylinders of the engine and tender is thus practically unlimited, but the limit has been found in some few