it becoming more and more saturated with the water retained. A not less effective and cheap absorbent is common salt; being very hygroscopic it withdraws the water and is dissolved by the water retained.

In the practice one or the other of these filtering materials, or a combination of both, is generally used. Fig. 98a and Fig. 98b show the arrangement of a filter. It consists of an upright iron cylinder, deeper than wide, with a conical or curved

bottom. The refined oil enters at the lowest point and runs off through an overflow pipe or still more suitably through a funnel. In Fig. 98 a, the oil enters the filter F through the pipe a. On entering the filter the oil pushes against the lid d, whereby a portion of the water is separated. The oil then passes through the bottom b,, which consists of a one-inch thick oak board perforated like a sieve and covered with linen for the retention of foreign bodies. Upon this bottom the filtering material is piled, the first layer consisting, as a rule, of saw-dust, next

comes a two-inch layer of common salt, then a layer of sawdust, and so on alternately up to a certain height. In many cases the filter is open on top, but to prevent saw-dust or salt from being carried along, and to accelerate the filtering process, an oak bottom b, arranged similar to b,, is placed upon the filtering material and can be firmly pressed down upon it by means of the screws S1, S2, etc. The oil penetrates the filtering materials, ascends to the funnel A, runs into the latter, and from there to the tanks. The oil is now ready for sale.

In refineries where filters are not used the oil is allowed to become clear in settling tanks. These are built of boiler iron and large enough to contain one charge from the agitator. In some of the larger refineries they are 40 feet in diameter and 10 or 12 feet deep. Before being used they are frequently given two or three coats of white paint. They are provided with a coil of hot-water pipe for the purpose of gently warming the oil in very cold weather. This greatly facilitates the settling of any water which may be left in it, and also its clearing. These tanks are often entirely exposed on all sides, and are simply provided with a roof to keep the rain out of them. By this exposure the oil, in good weather, becomes in a short time beautifully clear and brilliant. The tanks are also provided with a pipe connected with the steam pump, which admits of the oil being transferred from one tank to another used for the

same purpose. This pipe runs from the circumference to the centre on the bottom of the tank, and then straight up three or four feet along the rim; from the latter project a number of radiating pipes, all of which are perforated with holes, to admit of what is technically known as the

Spraying process. It sometimes happens that after the oil is in the form of finished product, perfect in color, brilliant and sparkling as could be desired, upon submitting it to inspection to ascertain the "fire-test," it falls short perhaps two or three degrees. A greater discrepancy than this manifests neglect of

duty on the part of the distiller, or mismanagement somewhere. Where the difference is not greater than this the difficulty is easily remedied by pumping the oil from one tank to another and allowing it to pass through the sprayer shown in Fig. 99. As every particle of the oil is thus exposed to the air in small streams, the small percentage of benzine it may contain is quickly volatilized and the fire test correspondingly

elevated. It is again tested, and if found satisfactory, it is ready for barrelling.

Barrelling.

The oil is seldom barrelled from the settling tanks, the latter being usually connected with the warehouse and sheds on the wharf by means of a pipe-line; this pipe-line may empty into what may be called a reservoir pipe, or a pipe of much larger capacity closed at both ends, with a number of small pipes inserted. To these are adjusted short sections of flexible gum hose supplied with a patented barrel-faucet.

An apparatus for filling barrels, which works automatically and requires no attention, is shown in Fig. 100. The petroleum coming from the tank enters at a and passes out at b. A valve

c in the interior of the apparatus regulates the flow, the lever d opening and closing the valves. At the moment of filling, the valve is opened by the lever d being suspended in a slit in the float s, which is also in the interior of the apparatus.

When the level of the oil reaches the float s, the latter is raised, whereby the lever d is released and forced back by the spiral spring into the position shown in the illustration, thus closing the valve.

On account of its shape, capacity and weight, the American barrel has been almost universally accepted as the commercial standard. It is made of American oak, all other varieties of wood, for instance European oak and beech, being inferior to it on account of their greater porosity and smaller weight. An excellent description of the manufacture and preparation of barrels was given a few years ago by Mr. Boverton Redwood, in his Cantor lectures before the Society of Arts, London, from which we quote as follows:

"The oak staves are purchased ready jointed and seasoned in Michigan, and the barrel heads are brought to the works ready glued up. The first operation in barrel making consists in fitting the necessary number of staves together in a thick wrought iron ring or hoop circling their lower ends. This is an operation requiring some experience and judgment. The embryo barrel is then placed in an iron cylinder and steamed, whereby the wood is softened. The staves are next encircled by a wire rope connected with an engine, and are thus bent into shape and drawn together, a second strong iron hoop being slipped over their upper ends to hold them in position. The barrel is then fired" by burning some readily combustible material in the interior, and the curvature of the staves thus rendered permanent. A number of extra temporary iron hoops of great thickness are next slipped on, and drawn towards the bulge of the barrel by means of an ingeneous arrangement of iron hooks or claws actuated by steam power. The final operation performed upon the staves consists in placing the barrel in a lathe, paring off the rough ends, and cutting the grooves for the heads.