Decorative headpiece featuring two putti flanking a central cartouche with a coat of arms.

THE AUTHOR'S PROPOSITION ON FIGURE VII.

A NEW GEOMETRIC LATHE, FOR REDUCING ANY CYLINDER OR CONE INTO AN OVAL FORM, WITH ITS ORNAMENTS, FROM ANY MATERIAL SUITABLE FOR TURNING.

Declaration of the same Seventh Figure.

Decorative drop cap 'H' featuring floral and scrollwork motifs.THE knowledge of this lathe will perhaps delight you if you understand its parts. The base is as in common lathes, but from the supports arise two immobile heads, so to speak, for others move, as one may see from the Figure. In the upper part of these is a slot, so that a board may be freely depressed and raised in it by the movement of the Orbs lying between the heads. For there are two Orbs, one Eastern and the other Western, which are disposed as in the compass for describing an Oval. To these Orbs adheres the mobile board already mentioned, in whose holes an iron instrument is placed; hence it happens that by the motion of the Orbs, it is depressed or elevated, so that the cylinder is turned into an oval shape. The rest are clear from the view of the Figure.

Addition.

This method of turning, which this lathe proposes to us, should not only not be despised, but rather received with a cheerful and grateful mind. For, not to mention the pleasure, which is certainly great, it brings greater utility to the workmen than they get from themselves, as they perform their work faster and better by this means than with the help of the many tools they use. But however it may be, in the immobile head, facing the East, a square hole is conceived, in which an oblong and square piece of wood is led and reduced, to join and disjoin the Poles supporting the cylinder, and also the mobile middle heads, already noted by the Interpreter. In the individual immobile heads themselves, both toward the East and the West, individual handle-like cranks are seen; which are turned in the round appearing holes; and thus they make the aforementioned poles, which support the cylinders, by passing through the two mobile heads, which are themselves perforated for this purpose, as it is sufficiently clear from the Figure itself that they are immobile. These handles are also bent as has been mentioned to confer greater force to the movement of the orbs they carry, for otherwise it would make no difference if they were straight. But the whole utility of this lathe depends on the orbs themselves, because they have their center in the same line with the cylinder, and are elaborated in such a way that they can be entirely adapted to freely provide any oval shape whatsoever, since the principal use is in leading and governing the iron instrument according to the operator's will. We must remember, however, that they must be placed in a similar position and with equal reason within those quadripartite toothed orbs which we see. The board sitting above them is perforated and has a sinuous slot in the middle like a serpent, so that it may admit the iron instrument according to the artisan's choice; for this is what guides the iron, while the hand does nothing but support it, and it finally rests on the orbs themselves, which by their motion either raise or depress it. Hence it happens that the instrument does not even touch the cylinder except when it is elevated or depressed through the board by which it enters. But it must not be overlooked that if other shapes are disposed here instead of the aforementioned orbs, such as those which the second compass describes, entirely similar figures will be turned by the same method.