their depth in casting to prevent turning when screwing up. But how many engines do we find fitted as here suggested? Few, we assure you.

If it is the correct and proper thing to screw 3 inch cap bolts into cast iron frames and blocks, and 1 inch and 11⁄2 inch stud bolts into castings in various places, what is the use of having head bolts with nuts? Why not, we say, if the practice is correct, make cast iron nuts for our large bolts, instead of going to the expense of forging them with such care as we generally exercise? No, we know that no sane man would think for a moment of making a cast iron nut for a 3 in. bolt, and yet he will screw that same 3 in. bolt into a casting where it was easy for him to use a T or square head, and this is not an overdrawn picture at all.

But it is to be hoped that this universal practice of tapping cast iron will be discontinued in the near future. Let the builders start with the determination that they will discard stud bolts in every case possible, and the result much needed will be reached.

The settings for shell tubular boilers must, for the sake of economy, be largely constructed of brick: but it is, we believe, the general opinion of our American engineers, that the ordinary

setting, as now constructed, has too many bricks in contact with the boilers.

In the first place, a boiler should in no way depend on the brick work for its support; but the lugs riveted on each side of the shell should rest on upright posts made of two pieces of channel iron, thimbled and riveted together, thus forming a light, strong, durable column, besides providing a complete universal adjustment for the expansion of the boiler, as the tops of the columns are free to sway in any direction; the bases being held in a cast iron foundation plate.

The bolts for holding fronts in position should not be anchored to brick work, but should be secured to the first set of channel iron columns supporting boiler.

Every fire-tube shell boiler should have two walls on each side of boiler, leaving a space of from 3" to 5" between boiler and inside walls, and 3" space between the two walls.

By this means a way is open for the expansion. and bulging of inside wall by heat, without affecting the outside wall in the least degree, while the non-conducting air-space is a great source of economy. Between the boiler and inside walls there should be a light flange of cast iron resting by wrought iron straps on the channel iron columns, and closing the space between boiler and walls at this point, thus preventing the

brick work from coming in contact with the boiler.

This is one of the most important items to be considered in setting any boiler.

The buckstaves for holding side walls in position should not be of cast iron, but of channel iron, with the flat web placed next to brick work, the lower ends bedded in concrete and the upper ends tied together (opposite sides), by bolts one inch in diameter passing over the return arch on top of the boiler.

The return arch should be made either of brick or blocks of asbestos, or some other nonconducting material, resting on T iron rafters, bent to the form of boilers; the return space under arch to be not less than 16" high in the clear for a 66" boiler, to admit of thorough cleaning and inspection.

The main bridge wall, directly back of grate bars, should be wide, for strength to resist the blows from fire-tools, and hollow, to admit air in sufficient quantity to ignite the escaping gases. Just back of this bridge-wall, there should be a small combustion-chamber, about one-half the capacity of the furnace where hard coal is used, and a little more than the full capacity of furnace where soft coal is the fuel. The object of this chamber, of course, is to allow the oxygen to freely mix with and ignite the unconsumed gases drawn over from the furnace. The remaining

Space under Recline

passage from combustion-chamber to return connection at the rear of boiler should be quite close to shell of boiler, on a 66" shell. This distance should be no more than 12" and no less than 8". The spaces and combustion-chambers under shell fire-tube boiler must not be too large, else there will surely be a loss from excessive radiation.

There should be cleaning-doors on one side of boiler where room will permit, but always at the rear of boiler, and these should be large enough to clean the tubes as well as the fire connection and spaces under the shell.

The cast iron fronts must not be too thin, on account of their liability to warp, but they can be well ribbed, and thus, in a measure, prevent this trouble. Where they are bolted together, the holes should be an eighth of an inch larger than the bolts, to allow for the expansion of castings. All fronts should be made in four pieces, planed or chipped together. When this method is observed, they will never crack at the doors or sides from excessive heat.

It

The setting should be done in a substantial manner, using hard brick with sharp lime mortar. The furnace and bridge walls should be laid with No. 1 fire brick, every fifth course a header. will make a good job and assist in keeping it clean, if the space back of bridge wall is smooth paved; and the outside appearance may be further improved by putting a stone coping on outside

walls. If the boiler is to connect with chimney, a breeching will make the connection across the front. If an iron smoke stack is used, do not let the weight of the stack rest upon boiler front, but put on a petticoat where it passes through the roof of boiler house, and let part of its weight rest upon the roof.

FEED AND BLOW-OFF PIPES AND VALVES.

An So horse-power economical engine will require an evaporation by the boiler of 1,800 lbs. of water per hour, for the cylinder alone; and an additional amount of at least 200 lbs. per hour for loss by radiation, etc.

The perfect feeding apparatus should distribute this 2,000 lbs. of water uniformly, as to time and quantity, through the space of sixty minutes, and into the body of water in the boiler at a neutral point or plane of temperature.

The feed pipe should not enter the boiler near the bottom for several reasons.

The first is the bad effect this method has on the fire-sheets of shell, by sudden contraction, as the water reaches the sheets where the fire is fiercest, at a temperature 150° below that of the water already in the boiler, assuming the feed water to be heated by heater to 180°. Another great objection to entering the boiler (with feed) at the bottom, is the matter of sediment, or, in many cases, quantities of mud, that rapidly col