SHAFT

In Architecture, that part of a column between the base and capital, sometimes called the trunk of the column. The shaft of a column always diminishes in diameter from about a third of its height. Sometimes it has a slight swelling {see Entasis) in the lower part of its height. In the oldest Doric columns, the diminution was so considerable as to give the column a conical appearance. In the Doric edifices at Athens, the upper diameter is not more than a quarter le than the lower diameter; in the temples of Jupiter Nemeus, between Argos and Corinth, not more than a fifth le . In Ionic and Corinthian columns, the difference of the upper and lower diameters varies from a fifth to a twelfth. The ancients seem to have regulated the diminution in some proportion to the absolute height of the column, for no particular law seems to have prevailed in terms of the lower diameter. Shaft. In Mines. A shaft or pit is a prismatic or cylindrical hollow space, the axis of which is either vertical or much inclined to the horizon. The dimension of the pit, which is never le than 32 inches in its narrowest diameter, amounts sometimes to several yards. Its depth may extend to 1000 feet, and more. Whenever a shaft is opened, means must be provided to extract the rubbish which continually tends to accumulate at its bottom, as well as the waters which may percolate down into it; as also to facilitate the descent and ascent of the workmen. For some time a wheel and axle erected over the mouth of the opening, which serve to elevate one or two buckets of proper dimensions, may be sufficient for most of these purposes; but such a machine becomes ere long inadequate. Horse-whims, or powerful steam engines, must then be had recourse to; and effectual methods of support must be employed to prevent the sides of the shaft from crumbling and falling down. lUre's Diet, of Arts, Sfc.) [s. 1123]