Meddelelser 2008 - Ole Rømers Venner

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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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