XIV. On a New Construction of the Going-Fusee. By G. B. Airy, Esq. 



Astronomer Royal. 



[Read March 2, 1840.] 



I should not have presumed to occupy the time of the Cambridge Phi- 

 losophical Society with a mere description of a mechanical construction, 

 if I did not conceive that it might possess some interest for them, first, 

 as a modification of or rather a substitute for a contrivance, whose elegance 

 and importance have been universally acknowledged, but which fails 

 (from practical reasons only) in certain cases. And secondly, as an object 

 of local interest, the only existing application of the new construction 

 being in the mounting of the magnificent telescope, which the University 

 owes to the munificence of the Duke of Northumberland. 



The object of the going-fusee is, as is well known, to maintain exactly 

 the same action (whatever its amount may be) upon the first wheel of 

 a clock, while the clock is being wound up, as while it is going in its 

 ordinary way : supposing that the time required for winding up is not 

 very long. 



It was invented by Harrison ; and has always appeared to me one of 

 the most beautiful of the many beautiful contrivances in a highly- 

 finished time-keeper. 



When I was arranging the clock-work for the Northumberland tele- 

 scope, I soon perceived that it would be necessary to depart from Harrison's 

 construction in the going-fusee part. This was rendered imperative by 

 the magnitude of the force which, as it appeared probable, would be re- 

 quired to maintain the motion of the clock. A strain of lOOlbs. on the 

 cord was to be provided for : and therefore the remontoir spring must 

 be strong enough to support lOOlbs. without breaking, yet sufficiently 



Vol. VII. Part II. EE 



