PLUMMET, PLumn.nutn, or PLUMB • LINE, an instrument used by carpenters, masons, &c. in order to judge whether walls, &c. be upright planes, horizontal, or the like. It is thus called from a piece of lead, " plumbum," fastened to the end of a cord, which usually constitutes this instrument. Sometimes the string de scends along a wooden ruler, &c. raised perpendicularly on another ; in which case it becomes a level. See LsvEt. PLUMMING, among miners, is the method of using a mine-dial, in order to know the exact place of the work where to sink clown an air-shaft, or to bring an adit to the work, or to know which way the load inclines when any flexure hap pens in it. It is performed in this man ner: a skilful person, with an assistant, and with pen, ink, and paper, and a long line, and a sun-dial, after his guess of the place above ground, descends into the adit or work, and there fastens one end of the line to some fixed thing in it, then the incited needle is let to rest, and the exact point where it rests is marked with a pen : he then goes on further in the line, still fastened, and at the next flexure of the adit lie makes a mark on the line by a knot or otherwise ; and then letting down the dial again, he there likewise notes down that point at which the nee dle stands in this second position. In this
manner he proceeds from turning to turning, marking doWn the points, and marking the line, till he comes to the in tended place ; this dohe,lae ascends and begins to work on the surface of the earth what he did in the adit, bringing the first .knot in the line to such a place where the mark of the place of the needle will again answer its pointing, and continues this till he comes to the desired place above ground, which is certain to be perpendicularly over the part of the mine into which the air-shaft is to be sunk.