202100An ESSAY
Draw the Line e c, equal to the Length of
11Fig. 68. the Style of the Horizontal Dial; and, at its
two Extremities raiſe the Perpendiculars e o
and c p: Then draw the Line c G, thro’ the
Point c, equal in Length to the Style of the
Dial to be drawn; making an Angle with c e,
equal to the Inclination of the Dial-Plane. Af-
ter which, draw the Line o G p, thro’ the Ex-
tremity G of the ſaid Line, perpendicular there-
to. This Preparation being finiſh’d, we uſe the
Operations of the precedent Problem, in making
E O and C P, in the Horizontal Dial, equal to
e o and c p of this Figure; and o p, in the Dial
to be drawn, equal to op of this Figure; in
which, the Point G is the Foot of the Style.
11Fig. 68. the Style of the Horizontal Dial; and, at its
two Extremities raiſe the Perpendiculars e o
and c p: Then draw the Line c G, thro’ the
Point c, equal in Length to the Style of the
Dial to be drawn; making an Angle with c e,
equal to the Inclination of the Dial-Plane. Af-
ter which, draw the Line o G p, thro’ the Ex-
tremity G of the ſaid Line, perpendicular there-
to. This Preparation being finiſh’d, we uſe the
Operations of the precedent Problem, in making
E O and C P, in the Horizontal Dial, equal to
e o and c p of this Figure; and o p, in the Dial
to be drawn, equal to op of this Figure; in
which, the Point G is the Foot of the Style.
If it happens, in the aforeſaid Preparation,
22Fig. 69. that the Line p o cuts the Line e c; E O muſt
not then be aſſum’d in the ſame Line, in the
Horizontal Dial, as otherwiſe it muſt have
been; but, in that Line, continued on the other
ſide of the Foot of the Style.
22Fig. 69. that the Line p o cuts the Line e c; E O muſt
not then be aſſum’d in the ſame Line, in the
Horizontal Dial, as otherwiſe it muſt have
been; but, in that Line, continued on the other
ſide of the Foot of the Style.
The Demonſtration of this Problem, is the
ſame as that of the precedent one; in conſider-
ing the Angle p o Q, equal to the Angle G c e,
which is equal to the Inclination of the Plane.
ſame as that of the precedent one; in conſider-
ing the Angle p o Q, equal to the Angle G c e,
which is equal to the Inclination of the Plane.
We might have further ſhewn the Uſe of
Perſpective, in facilitating the Operations of
Dialling: But this would be deviating from our
Subject; and ſo we ſhall content our ſelves with
this Short Eſſay, touching the moſt common and
uſeful Problem in Dialling.
Perſpective, in facilitating the Operations of
Dialling: But this would be deviating from our
Subject; and ſo we ſhall content our ſelves with
this Short Eſſay, touching the moſt common and
uſeful Problem in Dialling.