it in operation to be superior to any they have previously used for the purpose. By proper proportion they secure extremely rapid valve closure without jar, shock, or noise.

The vacuum which serves to close the valve is maintained in the chamber above the central post. As the piston descends, closing the steam valve, any small quantity of air that may have found its way into this chamber is displaced through the antomatic valve shown in the top post.

The cushioning is accomplished in the annular chamber at the bottom. The piston in falling is first partially obstructed in the tapered upper parts of the annular chamber; then, as it passes this tapered portion, it is more completely resisted, the only escape for the imprisoned air being such as is provided by the adjusting screw. By means of this screw, any desired adjustment of cushion can be made, interposed leathers preventing the parts from striking metal to metal while making such adjustment, or at any time while in operation.

BALL-AND-SOCKET-BEARING.

It will be noticed that the attachment of the dash-pot piston to the rod is by means of a balland-socket-bearing. This permits the piston to turn freely on the central post, thus promoting uniformity of wear, and increasing the durability of the parts.

In addition to permitting revolution of the piston, the ball-and-socket connection compensates for any slight fault in alignment, avoiding all danger of binding; it also forms an oil reservoir, from which the oil cannot leak, thereby insuring perfect lubrication.

The oil-hole in the top of the piston provides for conveniently oiling the other parts which move in contact.

ENGINE-FRAME.

The Girder Frame of this engine is of heavy weight, and carefully designed to resist the strains to which it is subjected. We believe that, with judicious distribution of metal, this type of frame is for a given weight the strongest, as it is certainly the most convenient, of any yet devised. Its peculiar elements of strength have sometimes led to such attempts at economizing in the use of metal as to reduce below proper limits the qualities of strength and stiff

ness.

An examination of any of the sizes of these engines will satisfy the most critical that no mistake has been made in that direction. The cost of the extra metal in an engine-frame, necessary to put its rigidity beyond question, is but a trifle compared with the advantages of that rigidity.

Unfortunately, an engine-frame may be of no more than half the weight required for stability,

without much danger of breakage. But with the light frame the inevitable springing throws the parts out of alignment at every stroke of the piston, resulting in unnecessary friction and destructive wear, and frequently in breaking some of the working parts.

These frames will stand up squarely to work under any steam pressure employed in practice, and under loads twice as great as their rated power.

With the Girder Frame, if the work is properly done, the aligment is perfect, and with ample wearing surfaces it will remain so indefinitely.

EXHAUST PASSAGE AND CYLINDER.

These were the first builders of this class of engine to recognize the importance, in an economical point of view, of keeping the exhaust steam separated from the walls of the cylinder. Their views were that this would result in increased economy, in that the exhaust steam when passing in contact with the cylinder robs the latter of heat, which must be restored by the admission of a greater quantity of steam from the boiler to do a given amount of work. This view they have demonstrated to be correct, and in all sizes of their engines the exhaust from each end of the cylinder goes to a common outlet at the centre, through passages entirely distinct from the cylinder proper.

CONNECTING-ROD.

Their connecting-rods are made with gib-andkey adjustment, which they find to be the most reliable. The standard length of their rods is six cranks. This, though somewhat greater than usually found, they consider is enough better to warrant the increased cost.

The evil of short connecting-rods in creating unnecessary friction, and increased wear and strains, is not fully appreciated. The increased friction due to short rods is a constant cost in coal, and shortens the life of all parts of the engine.

Beyond a certain length of rod further increase will result in but little saving, will unwarrantably increase the cost of construction, and introduce inconvenient features; these facts clearly point to a limit. This limit these builders have fixed at six cranks, or three times the length of stroke.

CROSS-HEAD.

The cross-head is tapered and secured by a cross-key. This method they prefer to the screwed end, from the use of which serious accidents have occurred.

Although by the taper wedges and screws the most minute and accurate adjustment of gibs can be made, when properly adjusted the whole has the rigidity of a solid piece of metal. There are no parts liable to work loose and cause delay and accident.

The gibs are lined with best anti-friction metal, and present large wearing surfaces, backed up against the possibility of springing, which is sure to result with overhanging ends.

PISTON AND PISTON-PACKING.

The weight rests upon the centre ring, to which the piston and follower are securely attached. When by wear of the bottom of the centre ring, and of cylinder, the piston gets below the centre, it can be accurately centred by means of the adjusting screws. This they consider absolutely essential in a horizontal engine, in which, owing to gravity, the bottom of piston and cylinder will be subjected to somewhat the most wear. As this occurs, unless there are means for adjustment, the piston-rod will wear out of truth, the stuffing-box will be worn down, and a strain thrown on the rod liable to result in its fracture, or in breakage of some of the connecting parts.

The centre ring carries the weight of the piston, and protects the head and follower from

wear.

It is necessary, for safety, that the centre ring be somewhat smaller than the bore of the cylinder. If turned round, as is ordinarily done, when placed in the cylinder, the bearing will be only in a line on the bottom. This will, from wear on a small surface, soon not only locate the