Modus erigendi machinas, quæ constant pluribus ordinibus telariorum.
Ex figuræ inspectione addisces modum erigendi machinas quæ constant pluribus ordinibus telariorum. Tabernaculum hoc nostrum indiget duobus tantum ordinibus; nam telaria propinquiora oculo exprimunt faciem externam, remotiora exhibent faciem internam. Ne autem lateant stipites quibus telaria sustinentur, medietatem telariorum adumbrare omisimus. Recta LS est linea plani, recta DG est linea horizontalis; ac punctum distantiæ quod cadit extra paginam in recta CG prolongatâ, debet esse remotum à puncto C, quantum in superiori parte figuræ quinquagesimænonæ, punctum distantiæ est remotum à puncto oculi. Eadem horizontalis DG secatur normaliter in C à recta EF, quæ est sectio externæ faciei tabernaculi, & ex C incipiunt divisiones in partes æquales pro reticulatione anterioris faciei telariorum, ut dicemus figurâ sexagesimasecunda. Recta IL quæ est sectio internæ faciei tabernaculi, distat ad libitum à recta EF cui est parallela. Porrò, per divisiones rectæ EF (ut vides in M, N, O) ex puncto distantiæ ducendæ sunt visuales ad rectam IL pro reticulatione aliorum telariorum: distantia enim DC facit ut augere oporteat ea quæ in telariis pinguntur, alioquin justo minora viderentur. Atque hinc dignosces, cur arcus qui in telariis anterioribus pertingeret solum ad B, in posterioribus elevetur usque ad H.
Figura sequenti proponemus modum delineandi faciem internam telariorum, adhibita reticulatione externæ faciei: ad intelligentiam verò illius methodi, fiat in hac figurâ recta HP parallela ad DC, ac recta BC dividatur in totidem partes æquales, in quot partes divisa fuerit recta PC.
The Sixty-first FIGURE.
The Manner of erecting Machines, that consist of several Ranges of Frames.
By casting your Eye on the Figure, you’ll readily apprehend the Manner of erecting the several Ranges of Frames. This Tabernacle last describ’d needs only two of them; the Frame next the Eye represents the outer Face, and the hinder Frame the inner Face thereof. I have here describ’d but the Half-Breadth of the said Frames, that you might have a Sight of the Poles and Braces which support them. The Line LS is the Line of the Plan, or Ground-line; the Line DG is that of the Horizon; and the Point of Distance, which falls without the Page CG prolong’d, is as far from the Point C, as the Point of Distance is from the Point of Sight in the upper Part of the Fifty-ninth Figure. The Horizontal DG is cut perpendicularly in C by the Line EF, which is the Section of the outer Face of the Tabernacle; and from the Point C begin the equal Divisions for the Net-work of the foremost Frame, as is shewn in the Sixty-second Figure. The Line IL, which is the Section of the inner Face of the Tabernacle, may at pleasure be set nearer or farther from the Line EF, to which it is parallel. By the Divisions of the Line EF (as M, N, O) Lines are drawn from the Point of Distance to the Perpendicular IL, for the Net-work of that Frame; for the Distance DC obliges the Parts of D to be painted larger, otherwise they will appear less than they really ought. And from hence you may discern, why the Arch, which in the foremost Frame would reach only to B, does in the hindmost rise up to H.
In the following Figure is shewn the Manner of delineating the inner Frame, from the Net-work of the outer Face; for the better understanding of which, make the Line HP in this Figure parallel to DC, and let the Line BC be divided into as many equal Parts, as the Line PC was.