Theatrum instrumentorum et machinarum Iacobi Bessoni Delphinatis ...

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THE AUTHOR’S PROPOSITION ON FIGURE II.

A NEW AND UNIQUE INSTRUMENT, SUITABLE FOR MEASURING ALL PARTS OF ANY PROPOSED BODY, TO UNDERSTAND THEIR SYMMETRY IN THE STRUCTURE OF THAT BODY.

Declaration of the same Second Figure.

Decorative drop cap 'D' featuring floral and scrollwork motifs.This instrument consists of two rulers, made of wood, or brass, or any other material; one of which, which shall be called the upper one, extends from the Angle of the East and South to the Angle of the West and North: the other extends perpendicularly from the North to the South. Each of these is divided into fifteen equal parts, and again each of those into five, so that in total there are seventy-five parts. On the upper ruler, the head of a nail appears, whose interior parts, as well as those of the whole instrument, are depicted particularly to the West: the first and more Southern part of which is the Alhidada alidade or sighting vane; the other part or Figure is the Head of the nail, on whose rim circle the parts of the Altimetric Scale, or of measures, are drawn. The third is the Tessella sliding block or square insert, which is placed into the slot of the inner and continuous upper ruler. In it is a hole, in which the part of the nail moves freely, which emerges from the other Tessella sliding block, similar to this one; which is placed in the continuous slot of the other Ruler. The remaining part of the nail with the fifth Figure is the Cochlea screw, by which the instrument is fastened. There is also in each ruler another smaller and narrower groove, by which the nail is led and returned; so that the Tessellae sliding blocks may move in the continuous slots. This, however, is very similar to the Euclidean Compass invented by our Author, and can be adapted to many uses, as I shall demonstrate elsewhere (God willing).

Addition.

ALTHOUGH this instrument is here divided into seventy-five parts, it can nevertheless be adapted to a greater or shorter length, just as each person might prefer and as their convenience allows. Furthermore, those two rulers (if you look at their shape) should be square, flat, and of such thickness that they can conveniently admit those four continuous slots through excellent workmanship, in which those very slots, as has already been declared above, the Tessellae sliding blocks may move easily and appropriately.

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LINES OF THE EAST

LINES OF THE WEST