XXV. Observations on the Errors in the Sea-Rates of Chrono- 

 meters^ arising from the Magnetism of their Balances ; 

 with Suggestions for removing this source of Error. 

 By William Scoresby, Esq. F. R. S. Edin. 



(Read April 15. 1822J 



JL HE value of the Chronometer for finding the Longitude at 

 Sea, being, by the experience of many years trial, fully esta- 

 blished, I am induced to offer to the Royal Society some re- 

 marks on the change of rate observed in this instrument, when 

 on ship-board. This change of rate, that had usually been 

 supposed to arise from the motion of the ship, has recently 

 been attributed, by Mr Fisher, who accompanied Captain Bu- 

 chan in his Voyage towards the North Pole in the year 1818, 

 " to the magnetic action exerted by the iron in the ship upon 

 " the inner rim of the Chronometer's balance, which is com- 

 " posed of steel." I apprehend, however, that it will be very 

 easy to show, that although the alteration of rate may be, and 

 most probably is, owing to magnetism, yet the magnetic ac- 

 tion of the iron in the ship, excepting in cases where chrono- 

 meters are placed in immediate contact with large masses of 

 iron, can contribute but in a very small degree to the error in 



y y 2 question. 



