BERN-Machine, the name of an engine for rooting up trees, invented by Peter Sommer, a native of Bern in Switzerland.

This machine is represented by a figure on Plate LXXXVIII. drawn from a model in the machine room of the Society for the Encouragement of Arts, &c. It consists of three principal parts; the beam, the ram, and the lever. The beam ABC, (No. 1.) of which only one side is seen in the figure, is composed of two stout planks of oak three inches thick at least, and separated by two transverse pieces of the same wood at A and C, about three inches thick. These planks are bored through with corresponding holes, as represented in the figure, to receive iron pins, upon which the lever acts between the two sides of the beam, and which is shifted higher and higher as the tree is raised or rather pushed out of its place. The sides are well secured at the top and bottom by strong iron hoops. The iron pins on which the lever rests should be an inch and a quarter, and the holes through which they pass an inch and a half in diameter. The position of these holes is sufficiently indicated by the figure. The foot of the beam, when the machine is in action, is secured by stakes represented at G, driven into the earth. The ram D, which is made of oak, elm, or some other strong wood, is capped with three strong iron spikes, represented at f, which take fast hold of the tree. This ram is fix or eight inches square. square; and a slit is cut lengthwise through the middle of it, from its lower end at K to the first ferule a, in order to allow room for the chain g h to play round the pulley K, which should be four inches thick, and nine inches in diameter. This ram is raised by means of the chain g h, which should be about ten feet long, with links four inches and three quarters in length, and an inch thick. One end of this chain is fastened to the top of the beam at C, while the other, after passing through the lower part of the ram, and over the pulley K, terminates in a ring or link represented N° 3, the two ears m n of which serve to keep it in a true position between the two planks of the beam. In this ring the hook P is inserted. The hook is represented in profile, N° 2, where F is the part that takes hold of the ring. But it must be observed that the parts of this machine, represented at N° 2, 3, are drawn on a scale twice as large as the whole engine. The hook F, N° 2, should be made of very tough iron, as well as the handle D, and the arch E c. This handle should be two inches thick at x, where it joins to the hook, and the thickness gradually lessen by degrees up to the arch, which need not be more than half an inch thick. On each side of the pin x, is a semicircular notch, x, y, which rests alternately on the pins when the machine is worked. The hole D, and the arch Ec, serve to fix a long lever of wood EF, N° 1, by means of two iron pins; and by this contrivance the lever is either raised or depressed at pleasure, in order to render the working of the machine easy in whatever part of the beam the lever may be placed: for without this contrivance the extremity of the lever EF, would, when the handle is near the top of the beam, be much higher than men standing upon the ground could reach. It must however be remembered, that the lever is often shortened by this contrivance, and consequently its power lessened.

The machine is worked in the following manner: It is placed against a tree, in the manner represented in the figure, so that the iron spikes at f may have hold of the tree, and the end of the beam A be supported by stakes represented at G. The iron handle, N° 2, is placed in the opening between the two planks of the beam, and the wooden lever fixed to it by means of the iron pins already mentioned. The hook F takes hold of the chain, and one of the iron pins is thrust into the outer row of holes, by which means the outer notch x will rest on the pin, which will be now the centre of motion; and the end of the lever E, N° 1, being pressed downwards, the other notch y, N° 2, will be raised, and at the same time the chain, and consequently the ram. The other iron pin is now to be thrust into the hole in the inner row, next above that which was before the centre of motion, and the end of the lever E elevated or pushed upwards, the latter pin on which the notch y rests now becoming the centre of motion. By this alternate motion of the lever, and shifting the pins, the chain is drawn upwards over the pulley K, and consequently the whole force of the engine exerted against the tree. There is a small wheel at L, in order to lessen the friction of that part of the machine.

From this account the reader will very easily perceive that the machine is nothing more than a single pulley compounded with a lever of the first and second order. It must however be remembered, that as the push of the engine is given in an oblique direction, it will exert a greater or lesser force against the horizontal roots of the tree in proportion to the angle formed by the machine with the plane of the horizon; and that the angle of 45° is the maximum, or that when the machine will exert its greatest force against the horizontal roots of the tree.