DOI Page / Citation link:
https://doi.org/10.11588/diglit.19574#0218
D I A 201
plumb-line to the other end of the meridian line on the floor,
and find a point on the deling directly over it, as you did the
former point, as at C; and through thefe two points B and C,
on the cieling, ftrain and ftrike a line blacked with a fmall-coal
or any other colour, as carpenters do ; and that line B C on the
ceiling fhall be the meridian line, as well as that on the floor.
Then faften a firing juft on the nodus, and remove that firing
forwards or backwards, in the meridian line on the cieling, till it
has the fame elevation in the quadrant on the clinatory above the
horizon, that the equinoctial has in your habitation; and,
through the point where the firing touches the meridian line on
the cieling, fhall a line be drawn, at right angles with the meri-
dian, to reprefent the equinoctial line.
Thus in our latitude the elevation of the equator being 38 de-
grees and an half; I remove the firing fattened to the nodus
forwards or backwards in the meridian line of the cieling, till the
plumb-line of the quadrant on the clinatory, when one of the
fides is applied to the firing, fall upon 38 degrees and an half;
and then I find it touch the meridian line at D in the cieling ;
therefore at D I make a mark, and through this mark llrike the
line D £, as before I did in the meridian line, to cut the meridi-
an line at right angles; this line fhall be the equinoctial line, and
ferve to denote the hour diftances, as the contingent line does
on other Dials, as you have often feen.
Then I place the center of the quadrant on the clinatory upon
the nodus, fo as the arch of the quadrant may be on the eafl part
of the meridian line; and under prop itfo, that the flat fide of the
quadrant may lie parallel to the firing, when it is ftrained be-
tween the nodus and the equinoctial; and alfo fo as the firing
may lie on the femidiameter of the quadrant, when it is held up
to the meridian line on the cieling.
Then, removing the firing the fpace of 15 degrees in the qua-
drant, and extending it to the equator on the cieling, where the
firing touches the equator, there fhall be a point through which
the I o'clock hour line fhall be drawn ; and, removing the firing
yet 15 degrees further to the eaftward, in the femicircle of por-
tion, and extending it alfo to the equator, where it touches the
equator, there fhall be a point through which the II o'clock hour
line fhall be drawn, removing the firing yet 15 degrees further to
the eaftward in the femicircle of pofition, and extending it to the
equator; there fhall be a point through which the III o'clock'
hour line fhall be drawn.
The like is to be done for all the other afternoon hours. So
often as the firing is removed through 15 degrees on the qua-1
drant, fo often will it point out the afternoon diflances in the meri-
dian line on the cieling.
Having
plumb-line to the other end of the meridian line on the floor,
and find a point on the deling directly over it, as you did the
former point, as at C; and through thefe two points B and C,
on the cieling, ftrain and ftrike a line blacked with a fmall-coal
or any other colour, as carpenters do ; and that line B C on the
ceiling fhall be the meridian line, as well as that on the floor.
Then faften a firing juft on the nodus, and remove that firing
forwards or backwards, in the meridian line on the cieling, till it
has the fame elevation in the quadrant on the clinatory above the
horizon, that the equinoctial has in your habitation; and,
through the point where the firing touches the meridian line on
the cieling, fhall a line be drawn, at right angles with the meri-
dian, to reprefent the equinoctial line.
Thus in our latitude the elevation of the equator being 38 de-
grees and an half; I remove the firing fattened to the nodus
forwards or backwards in the meridian line of the cieling, till the
plumb-line of the quadrant on the clinatory, when one of the
fides is applied to the firing, fall upon 38 degrees and an half;
and then I find it touch the meridian line at D in the cieling ;
therefore at D I make a mark, and through this mark llrike the
line D £, as before I did in the meridian line, to cut the meridi-
an line at right angles; this line fhall be the equinoctial line, and
ferve to denote the hour diftances, as the contingent line does
on other Dials, as you have often feen.
Then I place the center of the quadrant on the clinatory upon
the nodus, fo as the arch of the quadrant may be on the eafl part
of the meridian line; and under prop itfo, that the flat fide of the
quadrant may lie parallel to the firing, when it is ftrained be-
tween the nodus and the equinoctial; and alfo fo as the firing
may lie on the femidiameter of the quadrant, when it is held up
to the meridian line on the cieling.
Then, removing the firing the fpace of 15 degrees in the qua-
drant, and extending it to the equator on the cieling, where the
firing touches the equator, there fhall be a point through which
the I o'clock hour line fhall be drawn ; and, removing the firing
yet 15 degrees further to the eaftward, in the femicircle of por-
tion, and extending it alfo to the equator, where it touches the
equator, there fhall be a point through which the II o'clock hour
line fhall be drawn, removing the firing yet 15 degrees further to
the eaftward in the femicircle of pofition, and extending it to the
equator; there fhall be a point through which the III o'clock'
hour line fhall be drawn.
The like is to be done for all the other afternoon hours. So
often as the firing is removed through 15 degrees on the qua-1
drant, fo often will it point out the afternoon diflances in the meri-
dian line on the cieling.
Having