A rotary motion is communicated to the four screws simultaneously by the transmission arranged upon the frame. To this effect, the pulley, P, which receives the motion and transmits it to the saw, has its axle, _f_, prolonged, and grooved throughout its length in order that it may always be carried along, whatever be the place it occupies, by the hollow shaft, F, which is provided at the upper extremity with a bevel wheel and two keys placed at the level of the bronze collars of its support, G. The slider, D, is cast in a piece with the pillow block that supports the shaft, _f_, and the bronze bushing of this pillow block is arranged to receive a shoulder and an annular projection, both forged with the shaft and designed to carry it, as well as the pulley, P, keyed to its extremity. Now the latter, by its weight, exerts a pressure which determines a sensible friction upon the bushing through this shoulder and projection, and, in order to diminish the same, the bushing is continuously moistened with a solution of soap and water through the pipe, _g_, which runs from the reservoir, G'. The saw is kept from deviating from its course by movable guides placed on the sliders, D and D'. These guides, H and H', each consist of a cast iron box fixed by a nut to the extremity of the arms, _h_ and _h'_, and coupled by crosspieces, _j_ and _j'_, which keep them apart and give the guides the necessary rigidity. The shaft, _m_, mounted in pillow blocks fixed to the left extremity of the frame, receives motion from the motor through the pulley, _p_, at the side of which is mounted the loose pulley, _p_. This motion is transmitted by the drum, M, and the pulley, L, to the shaft, _l_, at the other extremity. This latter is provided with a pinion, _l'_, which, through the wheel, F', gives motion to the saw. The shaft, _m_, likewise controls the upward or downward motion of the saw through the small drums, N and _n_, and the two pairs of fast and loose pulleys, N' and _n'_. This shaft, too, transmits motion (a very slow one) to the four screws, _g_ and _g'_, in the interior of the columns, and the nuts of which are affixed to the sliders, D and D'. To this effect, the shaft, _q_, is provided at its extremities with endless screws that gear with two wheels, _q_', with helicoidal teeth fixed near the middle of two parallel axes, _r_, running above the table, B, and terminating in bevel wheels, _r'_, that engage with similar wheels fixed at the end of the screws, _g_ and _g'_.