This machine, according to its size, weight, and cost, is divided into Nos. 4, 5, and 6, capable of planeing metal from four feet long, by eighteen inches wide and high, to six feet six inches long, by twenty-four inches wide and high--and weighs respectively 1000, 2,600, and 3,500 pounds. The machine from which the design at the head of this paper is taken may be seen at No. 60 Beaver Street, New York. [Illustration: =NO. 2.--IMPROVED ENGINE LATHE.=] This again is a highly valuable and ingenious machine; its special operation is, as its name implies, the turning of any iron work to its required round circumference and requisite degree of polish, whether it is a perfect cylinder, or of various diameters at various points. By it, all round work for engines is formed and finished--as rods, shafts, and the like. The action of the machine is simple, easy and almost noiseless. The piece of metal is fixed in the spindle, shown in the cut above in contact with the right elbow of the spectator, and secured, longitudinally of the machine, on the sharp point proceeding from the fixture at the left end of the Lathe, behind the operator’s shoulder. To this, the object of operation, a rapid rotatory movement on its own axis is given by steam-power, and the cutting is produced by its rotation against two steel edges impinging on it laterally, and made to travel horizontally and longitudinally on a bed, so as to cut the bar, submitted to its agency, equally throughout all its length. This instrument is also directed by one man only, while acting with the combined power of very many, and performs its work with an ease equalled only by its great exactitude. [Illustration: =NO. 3.--IMPROVED GEAR CUTTING ENGINE.=] For the benefit of those of our readers, who have no previous acquaintance with mechanism, we shall merely premise that a gear is a wheel with a toothed circumference, like watch-wheels, or what in ruder mechanism are known as cogged-wheels; and those gears, known as level gears, are such as have the toothing on the circumference not perpendicular to the plane of the diameter, but at an acute angle to it, so that when two gears of a peculiar degree of bevil are set in contact, a horizontal rotatory movement may be communicated to one by a corresponding perpendicular rotation of the other. This will be rendered comprehensible by a careful examination of the motive power of the borer in the representation of the instrument, No. 5.