The Dragon Sun-Dial looks like the christian cross, but it has
nothing to do with that. Another name in use was shepherds sun-dial. It
measures the height of the sun according to the date. During the Middle Age,
these sun-dials were very popular because they were sturdy, easy to use and
did not need a compass. It is assumed, that this type was developped by Hermann
der Lahm (Herman the Lame) (1013-1054), a Benedictian monk from Reichenau at
the lake of Constance.
There is an engraved cylinder mounted over the tail of the dragon. This cylinder
is rotated until the mark underneath the wings points to the appropriate date.
The horizontal beam is pointed to the sun and the end of the shadow shows the
True Local Time.