Meddelelser 2008 - Ole Rømers Venner

These quotations may convince that Huygens strongly believed in the ultimate
supremacy of the balance spring over the pendulum for the best timekeeper at sea.
5. Description of the clock
As Figure I already showed, the recently discovered clock by Thuret has a brass case
in the shape of a cylinder. The diameter of the cylinder is 16.8 cm and its length 8.3
cm. The front door, provided with glass, and the tumed brass back door are hinged at
the left side as usual in French clocks; both are gilded. The case itself is of rather thin
red copper covered with grey fishskin (ray). The inner side is reinforced with a brass
ring to which a pair of lead plates are attached at the left side as a counterbalance of
the heavy spring barrel positioned at the right.
There can be no doubt that the clock was designed to be used on board of a ship
because the top of the case is provided with an iron ball enclosed by a brass cylinder
fbr free moving, see Figure l. This construction can be recognized as a contribution
of Alexander Bruce to the first seagoing pendulum clocks designed by Christiaan
Huygens.sE After the lattey's definitive return to The Netherlands, the device was
occasionally used by clockmakers who worked for Christiaan Huygens for similarly
shaped clocks made for general use on board of ships,
The gilt brass dial plate (diameter 16.0 cm) has three silver rings: the upper one for
the hours, the lower right one for the minutes and the lower left one for the seconds.
The plate is beatifully engraved after the best French tradition, with a border of
acanthus leaves enclosing flower scrolls and a mask in the area outside the rings. At
the top the name of the maker Thuret A Paris is engraved.
[Figure {. The movement of the Thuret clock]
Figure 4 reveals that the movement is driven by a going spring barrel. This is a clear
indication of the strong influence of Huygens on the clock's construction. As is well
known, Huygens' tnrst in the accuracy of the pendulum was so great that he
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