Full text: Gravesande, Willem Jacob: An essay on perspective

on PERSPECTIVE. P S, and making the Point p be the ſame as P. then join each Diviſion of this Line, to the
correſpondent Diviſion of the Line h i; and the
Dial ſought, will be drawn: p being the Foot
of the Style, and p s the Horizontal Line.

192.1.

Fig. 67.

193. Demonstration .

The Baſe Line is h i; p s is the Horizontal
Line; p the Point of Sight; and E O, or C P,
of Figure 66. is the Length of the principal
Ray.

193.1.

Fig. 66,
67.

Now, ſuppoſe the Plane p s h i, to be ſet per-
pendicularly upon the Horizontal Dial, in ſuch
manner, that the Line h i coincides with H I,
and the Point o with O. Suppoſe, moreover,
that thro’ the Extremity of the Style, which we
conſider as the Eye, Lines are drawn in the Ho-
rizontal Plane, parallel to the Hour-Lines of
the Dial; it is evident, that theſe Lines will
meet the Horizontal Line p s, in the Point al-
ready prick’d down; and conſequently , the Appearances of the Hour-Lines, are the Lines
joining the Diviſions of the Lines h i and p s.

193.1.

13.

194. Remark .

If the Line H I happens to meet the Meri-
dian; the common Method, by the Horizontal
Dial, is eaſier than this.

195. Prob . II.
123. To draw inclining Dials.

Theſe Dials are drawn in the ſame manner as
Vertical ones; the following Preparations being
firſt made.

Note to user

Dear user,

In response to current developments in the web technology used by the Goobi viewer, the software no longer supports your browser.

Please use one of the following browsers to display this page correctly.

Thank you.

powered by Goobi viewer