Meddelelser 2008 - Ole Rømers Venner

Meddelelser 2008 - Ole Rømers Venner

of Huygens might have had its origin in the fact that Thuret had recently succesfully

made some clocks provided with a pendulum attached to a smight spring instead of

the usual thread.{a

It is obvious that Thuret had strong commercial reasons to give in. On l5 February

1675, Huygens had obtained the exclusive right'to have made watches and clocks of

a new invention' for a period of twenty yeats.ot It is of interest to read that the inven-

tion consisted of a spring tumed as a spiral which regulates the rotations of a free ba-

lance, larger and heavier than in the usual works; by this, clocks constructed in little

will give very accurate pocket watches and, in larger designs, everywhere and in par-

ticular for finding the longutudes both at sea and on land. With his letter referred to

above, Thuret's exclusion from Huygens' general arrangements to make clocks and

watches as patented came to an end.

4, The significance of the new invention for marine timekeepers

As we just saw, the text of the patent explicitly included the right to make marine

clocks with a balance spring. [t is most likely that, in fact, this had been the major

reason for Huygens' efforts to invent a more precise clock not making use of the

pendulum. ln his notes discussed above, we find clear evidence for it. They include

drawings with two balances, rotating in opposite directions in order to minimize lhe

effects of movements. But perhaps more importantly is the fact that he drew two

versions of the construction: in his notes the escapement is, as usual, directly coupled

with the balance wheel (Figure 2) which became universally accepted in watches, and

in his Letter to the Editor published in the Journal des Sqa'ttants of 25 February 1675,

with an extra wheel between balance and escapement, see Figure 3.6 One may righr

ly ask why Huygens introduced the wheel between balance and escapement as it re-

presents an additional source of friction. Apparently he had the opinion that a lower

oscillation ttequency, with less frequent impulses given to the verge, results in a more

detached, and therefore more accurate, escapement. [n pendulum clocks he tried to

reach this with a long pendulum and in his new invention by a balance moving rather

slowly over a wide angle. In order to limit the angle over which the verge rotates, this


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