STATIONARY ENGINES.

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a large centre piece, and securely dovetailed into the rim at theextreme diameter.

The main part of the connecting rod is of oak, strapped withwrought iron from end to end, well bolted together, and in additionsecured with a strong hoop shrunk on at the middle. Blocks of castiron are fitted to the ends of the rod for the brasses to bear against,the blocks being bolted through and through the straps; and as bothends of the rod are forked, the brasses are adjusted with deep jibsand keys. The top end is placed between the beam, as in theprevious example.

The beam has a total length of 40 feet between the outsidecentres, and is so arranged as to give a stroke of 13 feet to thesteam piston and 12 feet to the air piston. It is cast in halves, eachhalf weighing 1 6y 2 tons, the total weight on the centre gudgeon,including all the minor details, being about 44 tons. The wall forsupporting the beam and its adjuncts is 7 feet in thickness, built ofstone accurately dressed; the pedestal on which the main pillowblocks rest is bolted down with twelve bolts, 3 inches in diameter,taking a wall plate, the extreme breadth of the lever wall, placedbelow the level of the floor, for the blowing-cylinder end.

The blowingcylinder is 144 inches in diameter, stroke 12 feet; andas the piston makes twenty double strokes per minute, the quantityof air discharged is nearly 54,28 3 cubic feet per minute, delivered ata pressure of 3^ lbs. per square inch. The area of the entrancevalves is 56 square feet, and that of the delivery valves 16 squarefeet. The cylinder is cast in two pieces, and is bolted down to thebottom plate, which is strongly ribbed in the casting, and arrangedwith a suitable number of openings for the air flap valves. Thisbottom plate is supported on pillars of cast iron at convenientdistances all round, which are stepped on a massive cast-iron plateresting on the top of the foundation, and to which it is bolted withlong bolts passing down through the foundations, and secured atthe bottom with keys bearing on a wall plate built into the stone-work. The cover is fitted with valve boxes, as in the previousexample, the flap valves beating against the angular sides of theboxes. The boxes are fitted with covers at the top, through whichthe inside of the cylinder may be inspected. There are also fittedat the top and bottom large entrance valves, placed verticallyimmediately over and under the discharge passages. The non-

return or discharge valves are placed in a line with and immediately

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