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Vertical Dials
This is the type
found on the walls of churches and other buildings. Vertical sundials
may be direct south dials if they face due south (in which case the
gnomon will be at an angle equal to the co-latitude of the place, and
the hour lines, if delineated for local time at the place, will be
symmetrical about the vertical noon line).
If they do not face directly south, they are described as declining
dials, and in this case the gnomon will be at a lesser angle than the
co- latitude, and the hour lines will generally be grouped more
tightly in the morning hours, for south-east decliners and,
conversely, grouped in the afternoon hours for south-west decliners
Polar Dials
Polar dials have
the dial plate fixed parallel with the earths axis. The gnomon is
parallel to the dial plate, typically the edge of a rectangular plate
fixed to the dial plate. The hour lines are parallel to the gnomon and
thus to each other.
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