Inclination and Levels.-The boilers should be set in the setting" at an inclination of 1⁄2 inch in 10 feet toward the blow-off cock.

The dead plate should be set 2 feet — 8 inches above floor of stoke-hole.

The best position for the fire-level inside flues is about 20 inches to 22 inches from the interior top of a flue. Fire-bars should be inclined 1 in 10 to 1 in 12 away from the stoking-door. Length of dead-plate, 10 inches. Thickness of fire-bars, 1⁄2 inch to 3/4 inch. Spaces between them, 3% inch to 1⁄2 inch. Fire-doors about 16 inches × 13 inches.

Water level should be set for a minimum of 4 inches above flue top, and an average of 9 inches.

Gauge glasses should be 10 inches long.

Oval man-holes are usually 18 inches x 15 inches.

covers indiscriminately a The leading types are the The former has the usual

Vertical Boilers. This term is applied to boilers in which the shell stands vertically, and large variety of internal design. cross-tube and multitubular. circular internal fire-box, across which are fitted as many large water-tubes as can be conveniently arranged. These greatly add to the efficiency of the boiler, and are better when made of a taper form or set at a slight angle from one side to the other, thus allowing the steam particles or bubbles to have a natural ascent.

This form of boiler is very simple and substantial, and easier to clean than most other types. Like all ordinary vertical boilers, its weak point is the passage of the up-take through the steam space, rendering it liable to burn out in time.

To overcome this objection quite a number of patented and non-patented arrangements of parts have been devised. Some of these are meritorious. All should be looked into to see that they afford no corners for the reception of de

posit, and that all parts are accessible to cleaning and repair.

The same remarks apply to the numerous forms of multitubular vertical boilers, some of which contain, in proportion to their sizes, an immense heating surface. Of these the boilers of fire-engines are examples, the fire-boxes of which are crossed by a multitude of small brass water-tubes, effecting very quick steam-raising.

The well-known "Field" drop-tubes have found favour, but rapidly burn out when used with water in which much deposit occurs.

For small powers, up to 15 horse-power, the vertical boiler is very suitable, and its convenience for placing and absence of brickwork render it very simple of adaptation. Wherever possible it should be clothed well with one of the many non-conducting materials.

VERTICAL MULTITUBULAR BOILERS.

Some improved vertical boilers are made with an up-take brought over to one side, from which horizontal fire-tubes extend to a smoke-box situated at one side. In these all

7 &

I II

21

£65

4 3 I

$375

3 3

42

3 4
38

45

=

$490

54

the heated surfaces are under water, and a large addition is made to the life of such a boiler by this means.

A sample list of such boilers will serve to afford a comparison of cost and proportions.

SPECIAL VERTICAL MULTITUBULAR BOILERS.

No form of boiler has received more attention at the hand of inventors and improvers than the vertical, and very many types are now offered on the market. The particular points to be sought in a selection are, accessibility of the tubes and interior, unrestricted steam space, and a minimum of heated plate surface exposed to steam and not to a covering of water.

CHAPTER XXVII.

HORIZONTAL MULTITUBULAR BOILERS.

THESE boilers are, in their simplest form, shells pierced from end to end by a quantity of tubes. The boiler is then set in a brickwork "setting," and one great advantage the arrangement possesses is that the fire-grate area, which is below the body of the boiler, may be of any reasonable size. Thus the form of boiler becomes suited to the burning of poorer fuels in an economical manner. It may also be set in a flue leading from a furnace, and in this manner make effective use of waste gases. For general conditions, and with good fuel, its use is superseded by the water-tube or tubulous boilers, which exceed it in efficiency though not in simplicity.

English practice is to use a shell of a length not exceeding double the diameter, such as the following:

HORIZONTAL MULTITUBULAR BOILERS FOR 75 LBS. WORKING Pressure.

In the United States, where these boilers are in extended use, their proportions are of endless variety, and they are

often made with tubes of large size, suited to the burning of poor fuels and sawdust. The following are about average sizes, and particulars of the furnace and smoke-box arrangements. It will be seen that they are longer in proportion to their diameter than in English practice.

HORIZONTAL MULTITUBULAR BOILERS.

AMERICAN PROPORTIONS.

The smoke-box is of heavy sheet iron, with a heavy castiron front-plate with double folding doors swinging horizontally, and a cast-iron angle-plate extending around the smoke-box, and made to fit against the face of the brickwork, the bottom of it resting on the furnace front and supporting the smoke-box.

The furnace front is made of cast iron, the main web or plate, with the furnace and ash-pit doors, being set back about seven inches from the face of the brickwork, and