The tanks are so connected, however, that the pipe i will be air-locked between the points m and o, the cause of the lock being the pocket p, made in order to clear the lower flange of a steel beam q; and the loss of head in B will equal the vertical height of the air column as represented by the distance n.

There are several ways by which this air lock may be avoided; one method is to make a connection to the side of the tank A, as shown by dotted lines at r, instead of to the bottom. Another method is to leave the bottom connection as it is, and run in a small air-relief pipe, the upper end of which is bent over the tank B and the lower end joined to the highest point of the air bound part of i, as shown by dotted lines. Either of these simple changes will effect a permanent remedy.

USEFUL INFORMATION FOR PLUMBERS.

LEAD BURNING.

Lead burning is a process of joining pieces of lead by molten lead instead of soft solder. Ordinarily the edges of the pieces are cleaned and lapped and then fused together by the heat of a hydrogen flame. When it is necessary to reenforce the seam with more lead, the flame is fed from a stick of lead.

A lead-burning machine of the generally accepted form is composed of a hydrogen-gas generator, an air tank, and an air pump. The generator is divided into two compartments, the upper one being open at the top and the lower one closed air-tight. They are joined together by a lead pipe extending nearly to the bottom of the lower chamber. The lower chamber is furnished with a perforated shelf about 2 in. from the actual bottom. Commercial zinc is laid on this shelf through a screw-cap opening placed on top. About 3 oz. of zinc will furnish 1 cu. ft. of gas. The charge of zinc should be about 20 to 25 lb. for a machine that is intended to run all day. A mixture of 5 parts of water to 1 part, by volume, of commercial sulphuric acid, is poured into the upper chamber. This flows into the lower chamber, where it rises until it acts

on the zinc, when hydrogen gas is liberated and a pressure is formed in the lower chamber that forces the liquid back into the upper chamber. The column of liquid in the connecting lead pipe forms the desired pressure in the gas chamber. Gas is conveyed to a breeches pipe through a rubber tube, and air from the air holder that is loaded with weights to give the desired pressure is conveyed by another tube to the same

breeches pipe. Two stop-cocks on the breeches pipe are used to regulate the flow of air and gas into the mixing tube, which is generally held in the hand, so that the proportions of gas and air will be just right for a lead-burning flame.

The process of burning is as follows: First, thoroughly clean the edges of the lead to be joined; adjust the blowpipe flame so that it will be about 1 in. long, needle-pointed, and burning silently. Apply the flame so that the inner cone will touch the surface of the lead. The intense heat will melt the lead and cause the edges to flow together. The flux commonly used for this work is known as Yaeger's salts. Expert lead burners, however, operate without a flux when they use a hydrogen flame. The flux is generally used when an ordinary air-and-gas flame is employed. The illustration shows a good example for practice in lead burning. Two pieces of sheet lead are prepared by planing the edges to be joined straight and square, and shaving the top surfaces clean about in. wide on each side of the butt joint; then the edges

are butted together, and the sheets are firmly secured to a board. The flame is then applied, as shown, and it is fed from a lead stick held in the operator's left hand. This stick is about in. or more thick, triangular in section, and shaved clean. With the point of the inner flame a few drops of lead are melted off the stick and allowed to fall squarely on the seam. The flame should instantly follow these drops and fuse them to the sheet lead. A section through the seam, when burned, is shown at b. It requires considerable practice to do this kind of work. Repeated failures may be expected at first.

RECIPES, TESTS, AND WORKSHOP WRINKLES.

To Remove Grease From Marble.-Apply to the grease spots a little pile of fullers' earth, or whiting, saturated with benzine, and let it remain 2 or 3 hr.; then wash off.

To Clean Marble.-Rub the marble well with a paste made by mixing with water 5 parts of soda, 2 parts of powdered chalk, 2 parts of powdered pumice stone; then wash the slab with soap and water.

Removal of Rust From Iron.-Oxalic acid will dissolve and remove rust from iron without injuring the iron.

Wiping Joints on Tin Pipe.-Joints can be wiped on blocktin pipe by using a solder composed of 3 parts of tin, 5 parts of lead, and 3 parts of bismuth; bismuth solder of this proportion melts at 2020 F. The composition and melting point of other bismuth solder can be found in the following table:

Cast-Iron Pipe Joints.-These may be made with soft pig lead calked into the hubs, or with rusted iron chips. When rust joints are used, they are made by filling the hubs with a cement made with 18 parts of water, 2 parts of sal ammoniac, 80 parts of iron chips.

To Galvanize Cast Iron.-First, cleanse.the casting thoroughly by immersing it, for a few hours, in a bath of 1 part of muriatic acid and 2 parts of water. Then remove the casting and scrub thoroughly with a brush and fine sand, after which wash with hot water. When the casting is clean, dip in a solution of sal ammoniac and hot water, ib. of the sal ammoniac to the gallon. Dry quickly and dip in zinc bath.

To Galvanize Wrought Iron.-Immerse in a bath, consisting of 1 part of muriatic acid and 4 parts of water, long enough to break up the scale; remove from the bath and clean with brushes or scrapers until the surface is free from scale or dirt. Then dip in another bath of muriatic acid and water consisting of 1 part of acid to 4 parts of water, with 1 oz. of sal ammoniac to the gallon of solution. Dry quickly and thoroughly in a hot oven or on hot plates and dip in a zinc bath.

Zinc for galvanizing should be so heated that it will have a clear, shining surface. The dross should be skimmed away and a little powdered sal ammoniac sprinkled on the surface occasionally to clear it.

If the surface of the iron is oily, first boil it in caustic soda or lye, to remove the oil. Then dip it in the muriatic-acid solution to remove the scales. Care should be taken to see that no moisture remains on the article to be dipped. Very little moisture will cause an explosion of steam bubbles that will scatter the molten zinc in all directions.

To Tin Iron Castings.-Cleanse the castings by immersing in a bath of diluted sulphuric acid mixed in the proportion of 1 part of acid to 20 parts of water, and scour with sand if necessary. After cleansing, boil the castings in a concentrated solution of stannate of soda with a quantity of granulated tin.

To Tin Wrought iron.-Wrought iron is tinned by first removing the scale, and then immersing the articles in a

pickle of sulphuric acid, finally dipping the iron in a pot partly filled with pure tin, over which is placed a layer of palm oil or tallow, to protect the tin from the action of the air and act as a flux. When the articles have been thoroughly coated, they are removed and allowed to cool, after which any grease is removed by rubbing in bran. Such small articles as rivets and tacks are taken out of the melted tin with a perforated dipper and the melted tin allowed to drain off, when they are thrown against a perpendicular sheet of iron to remove any superfluous tin that may adhere.

Paint for Galvanized Iron.-To prevent paint from scaling off galvanized-iron surfaces, the iron should be exposed to the weather long enough for the grease to wear off, after which it should receive a coat of paint mixed as follows:

Raw oil
Boiled oil
Liquid dryer

Dry metallic paint

1 gal. 1 gal.

gal.

20 lb.

To Color Solder.-Soldered seams on copper can be colored to match the copper by brushing the seam with a preparation made of pt. of water to 1 oz. of sulphate of copper in crystal form.

Plumbers' Soil.-To make plumbers' soil, dissolve 2 tablespoonfuls of glue in 1 qt. of boiling water, or stale beer, and beat into the mixture 1 lb. of lampblack and a tablespoonful of powdered chalk. Heat the soil each time it is used.

Plumbers' Paste.-Mix flour and water quite thin, beating all lumps out. Sprinkle a little pulverized alum, which will preserve the paste a month or more. Thicken slowly over a

fire.

Simple Tests for Sewer Gas.-Sewer gas is a mixture of several gases that emanate from decomposing animal and vegetable matter in sewers. The principal gases are sulphureted hydrogen, ammonia, and carbonic acid. A test for sulphureted hydrogen is a piece of blotting paper dipped in a solution of plumbic acetate; this is turned black on exposure to .the gas. For ammonia, a strip of red litmus paper will turn blue or yellow, and a strip of yellow turmeric