PIPES, SFIEET IRON. Sheet iron pipes of a new manufacture have lately been introduced into England, from France, where they have been in use for several years. They are made of sheet iron, which is bent to the required form and then strongly riveted together ; after which they are coated with an alloy of tin, and the longitudinal joints are sol dered so as to render them both air-tight and water-proof. In order to give them more stiffness, they are next coated on the outside with asphalt cement, and, if they are intended to be used as water pipes, the inside is also with bitu men, which resists, like glass, the action of acids and alkalies. They are so elastic that they will bear a considerable deflec tion without injuring the pipes or caus ing any leakage at the joints. The verti cal joints screw together in the same manner as cast iron gas-pipes. These pipes have been used for water, for gas, and for draining, and are found to be more economical than cast iron, besides being less liable to leak, and for water pipes they are more healthy than the common ones.
Iron pipe coated with glass.—At a late Soiree of the President of the Society of Civil Engineers, London, some speci mens of iron manufacture were exhibit ed, coated with glass, from the Smeth wick Iron Works of Messrs. Selby and Johns, near Birmingham, and which would appear to be the very desideratum so long sought for. In the process of coating plates, corrugated or plain roof ing, tiles, tubing of all kinds and dimen sions, frying-pans, grid-irons, sauce-pans, kettles, caldrons, or boilers, in lieu of coppers, and a host of other implements, domestic, agricultural, and manufactur ing ; the article is first thoroughly cleansed in an acid solution, to free it from every particle of grease, similar to the preparation for tinning, zincing, &c. It is then covered with a glutinous pre paration, over which is laid a coat of glass, ground to a fine powder.
The article is then introduced into a furnace of peculiar construction and suffi cient temperature, in which the glass is fused, and the intermediateglutinous matter being evaporated, the glass fills the external pores of the metal, and becomes firmly united to it ; as the manipulation becomes facilitated by prac Lice, it is probable that the cost of a glass coated iron material, of these common kinds, will be but a mere nominal trifle more than the plain articles themselves.
The dinner plates shown were four ounces lighter than an earthenware plate of the best construction, size for size. The foliage and designs are in relief, and are executed by a kind of stenciling ; one color being put on, it is transferred to the kiln and fixed; then, when cold, another color is added, again fixed, and so on until the whole pattern is applied. PIT COAL. Under the article COAL, some remarks connected with the nature of the deposit, and the extent of its beds in this country are given. Under the present will be considered chiefly its con nection with the basin form, and the want of horizontality of the beds, which induces the necessity of sinking shafts, and mining, to bring it to the surface. The majority of the pit coal is found in the carboniferous limestone formation, or that of the system of rocks found in Northern Pensylvania, and which lie im mediately above the old red sandstone, the Potsdam sandstone of the New York system of rocks. It is rare indeed to find coal in a stratum rock higher than the mountain limestone, although it does occur in the oolitic or upper secondary rocks. Such is the position of the bed of coal at Richmond, Virginia.
The simplest form of a coal-field is the entirely basin shape, in which the beds crop out all round, and dip down toward the centre.
These basins are generally elliptical, sometimes nearly circular, but are often very eccentric, being much greater in length than in breadth; and frequently one side of the basin on the shorter dia meter has a much greater dip than the other; which circumstance throws the trough or lower part of the basin conca vity much nearer to the one side than to the other. From this view of one entire basin, it is evident that the dip of the coal strata belonging to it runs in 01.po site directions, on the opposite sides, and that all the strata regularly crop out, and meet the alluvial cover in every point of the circumferential space, like the edges of a nest of common basins.