The accompanying engraving illustrates an apparatus designed by Messrs. Thomas Wood&Co., of Twenty-second and Wood Streets, Philadelphia, Pa., for dyeing warps indigo, blue, and black. The colors are formed by passing the warps through the liquor contained in a series of from four to fifteen vats, according to the quantity of warps to be dyed and the shade required. The warps pass from the inside boxes through the machine in the first vat and are then delivered into the outside boxes. The boxes are then shifted, the dyeing machine is lifted up and moved along, by means of a pulley block and truck, as shown in the cut, to the second vat; the warps make the passage through the liquor in this vat in the same manner, and so on through the series of vats until the proper shade has been acquired. When there is a large number of vats, two or more machines are employed, the one following the other. This process is simple and economical, and gives very superior results. Messrs. Wood&Co. also make machines fur dyeing fancy colors, with a capacity to work four, six, or eight warps at a time. The carrier rollers of these machines are copper, and the squeezing rollers are made either of wood, iron, or iron covered with rubber.