Theater of Mathematical and Mechanical Instruments

ends with a counterweight original: "contrepois", in order to return the movement that the worker has made with his foot in the stirrup original: "l’estrieu" attached to the beam. To this beam is fixed the end of the tool's handle, which has free movement from East to West and back again. Now, when the worker pulls the cord, he lifts his foot, and the counterweights that pull the beam push the iron against the work-piece; and when he lets go with his hand, he presses with his foot to withdraw the iron. From this, the curious reader will be able to understand the utility of the machine.

PROPOSITION X.

A fourth type of lathe, and one not yet seen, which serves to polish and cut marble into slabs and tables (as well as any other kind of hard stone) for the ornaments of sumptuous and magnificent buildings.

DESCRIPTION OF THE TENTH FIGURE.

THIS machine is not strictly a lathe original: "tour", given that the effect of a lathe is that by its means the iron or tool goes around the piece being turned; however, it is so called because of the similarity of the movement, which is a back-and-forth motion. But without dwelling on the suitability of the name, if we understand its properties, the description of the parts that compose it will be more desired. Now, it can serve (as the proposition says) those who are involved in polishing or cutting stones, as well as those who similarly smooth pasteboard original: "carton": and in general all those who use a polisher, each being able to adapt it to their whim, once they understand its parts, which are as follows.

FIRSTLY, the support or assembly that sustains the rest of the parts in which the movement and use of the instrument lie, is square and long, in the manner of a worker's workbench original: "establier de manouurier", being nevertheless firm and secure, both to support the weight and to endure the violent movement that occurs when it is in use. In the southern part appears a screw original: "vis", having a crank original: "signole" at its eastern end, by means of which it is driven: and around this screw is a nut original: "escroüe" that goes back and forth around it from East to West, and vice versa: being however held in place by a piece of wood that goes from it toward the North-East angle. To this piece of wood is another, parallel and similar, toward the West, joined to one another toward the North-East angle by three other pieces: one being where the worker is seen, and the two others at the ends of the assembly of those cross-sticks that are commonly called a scissor-linkage original: "happeuilain," a colorful term for a pantograph or lazy-tongs mechanism, and which I have named a Sautereau Sautereau: Literally "grasshopper," here referring to a hinged linkage that extends and contracts like the legs of an insect. And the first two pieces of wood are thus joined to each other in a frame, so that, being held in place, they neither approach nor move away from each other, because at their southern ends is a rocker original: "tour" turning on two pivots, much like those at the back of carts on which hay or grain is carried. Through this rocker passes a straight piece of wood which has a pierced semi-circle original: "demi orbe" toward the South, and a cross-piece toward the Northern end, so that it is like a T. And the said piece thus made is called a balance original: "balance", because the weight of the semi-circle returns that which the man first pulls toward himself. The northern part of it is called the head, which has two rings, into which enter two iron arcs, which end near the wood of the frame assembly: which wood is the second, starting to count from the North, and at which the sautereau ends, having there its first peg, from which it comes out to go toward the arcs of the head of the balance, to which it is attached: so that when the balance approaches the worker, the sautereau contracts: and when it moves away, it pushes out, because as it approaches it causes the arcs attached to the sautereau to widen, and as it moves back it narrows them, the nature of the said sautereau being such that when one widens its first feet, it contracts and shortens; and when one narrows them, it lengthens. Now at its northern end is the polisher, or cutting iron, which the man guides with his right hand, pulling with his left a cord that corresponds to the balance attached to it 16 feet away from the rocker, pulling toward the South, by means of which the movement is made. For the balance, because of the weight of its base, always pulls perpendicularly toward the ground, from which it follows that being pulled by the cord, it seeks to return to its place: which, being prevented by the sudden pulling of the worker, puts it in motion, so that it makes the cutter or polisher go back and forth briskly by means of the sautereau. This is the whole subtlety of the machine. As for the screw, it only serves to change the position of the frame, when one has polished or cut enough in one place, the worker going to turn it, having put his hand to the crank, in order to then begin again and do as described above.