BARREL. This article, as made by coopers, is too well known to need a de scription; but the air and watertight metallic barrels employed in the British navy for preserving provisions, from their peculiarity of structure and utility, require a place in this work. Those which we shall describe are of the most improved kind, and were patented by the late Mr. Robert Dickenson, of the Eagle Foundry, Southwark. These barrels are made of wrought iron, of a cylindrical form, with a seam, soldered or rivetted, in the usual way. To strengthen the figure, and adapt it for the reception of the heads, a strong iron hoop is rivetted to each end of the cylinder. These hoops are prepared at the iron works, by rolling them into the form of a rebate, shown in section at b, Fig. 1. By this diagram it is also shown that the hoop is fastened with its thickest part against the side of the barrel a, about an inch below the extreme edge of the same ; thus forming a deep groove between the sides of the barrel, and the thinnest part of the rebated hoop, for the reception of the flange of the bead e, which appears to be made by bending the periphery of the circular iron plate to a tight angle with its plane. Previous to the driving down of this head, a sort of pack ing, composed of hemp-bands, or currier's leather-shavings, is to be rammed into the groove, so as effectually to exclude both air and moisture. To secure the bottom head in its place, the thin projecting edge of the hoop is to be ham mered down upon the bottom, and over this is to be rivetted a flat iron ring, to serve the purpose of the ordinary chimes of barrels, the exterior edge of which should extend a little beyond the periphery of the cylinder, to defend the sides of the barrel in rolling it. The upper head of the barrel is so constructed as to be removable at pleasure, the hoop which circumscribes it being the same as that on the bottom ; but, instead of being hammered down, it is left erect, as shown at Fig. 2. The head is placed also within a similar groove, and is fastened down by means of a number of latch-bolts. These latch-bolts are attached to the head, or movable cover, by means of a pivot at one end, upon which they turn, and are driven sideways into long slots made through the projecting hoop, which slots are not made in a parallel line with the top of the cask, but aslant, so that when the latch-bolts are driven into them by a hammer, they draw the flanged head into the deep groove, which, being previously packed in the manner before-mentioned, makes the junction perfectly air and water-tight.
This kind of cover, likewise, admits of its being very readily removed, by driving back the latch-bolts with a hammer ; and the inconvenience formerly experienced in the smallness of the apertures in air-tight vessels, is herein com pletely removed, the opening being as wide as the barrel itself, so that larger matters may be stowed in it, and the packing and removing of the contents greatly facilitated. Metal casks, heretofore employed for similar purposes, were usually coated with paint to prevent oxidation, and render them water-tight, which was found to communicate a bad flavour to the flour, biscuit, or other materials which they contained. To remedy this inconvenience, the patentee coats the barrels, both inside and outside, with any of the well-known water proof compositions, which, while they effectually prevent oxidation, will not communicate any unpleasant taint to the articles of food, even in the hottest climates. The patentee has selected the following :—To 1 pound of caoutchouc (Indian rubber) add 8 oz. of black resin, and 2 oz. of Venice turpentine; let the caoutchouc be cut into small pieces, and expose the mixture to a heat of 1600 for the space of 24 or 36 hours. When dissolved, it is to be spread upon canvass, or other fibrous material, and then passed between cylindrical rollers to give it an even consistency. With this material the ban els are to be coated both within• and without, except in the case of dry goods, such as biscuits, flour, &c., when the coating of the exterior alone is considered sufficient, and the interior surface of the iron may be bronzed in the same manner as gun barrels. For oils, tar, varnish, &c. the insides of the barrels have no coating, those materials being, of themselves, preservatives against oxidation. In some cases of dry goods, the inside may be coated with the thinnest and cheapest woven material, or even paper; and these may be attached, by any cheap kind of cement, that will effectually exclude the air and moisture.