62 On the Rates of Chronometers. [No. 1. 



these poles with respect to the magnetic meridian, Mr. Varley moreover 

 found that every new balance which he tried was already more or less 

 polarized ! 



His communication dates in 1797, but from this time to 1820 which 

 is the date of Mr. Fisher's* paper read by Mr. Barrow to the Royal 

 Society (Phil. Trans. Vol. CX.) I have not found any farther pub- 

 lished notices of this phenomenon, though skilful navigators were well 

 aware of the tendency of Chronometers to take on " sea rates ;" usually 

 accelerated ones ; and the practice was both to correct by the run to 

 Madeira or Teneriffe if seen, and to give a " lunar rate" also. Mr. 

 Coleman, an old Company's Officer and now an eminent teacher of 

 Mathematics in London, has given a number of tables of rates given 

 on shore with those found at sea with the Chronometers of various 

 ships, mostly of those of the E. I. Company, from 1802 to 1820; 

 distinguishing the iron from the copper-fastened vessels, but he draws 

 no general results. 



Mr. Fisher's paper, after shewing the tendency of Chronometers to 

 take on accelerated rates, describes the remarkable effects on the rates 

 which were found on landing them on Spitzbergenf which with one 

 amounted to a difference of thirteen or fourteen seconds daily, and 

 another returned to its exact London rate ! Mr. Fisher also quotes 

 Lieut. (Sir John) Franklin, as remarking that it is to this circumstance 

 we must attribute the error of the whole of the line of Coast on the 

 West side of East Greenland being laid down 1^° too much to the 

 Westward by Captain Phipps (Lord Mulgrave) in 1 770 ; and that in 

 the first trial of Harrison's Timekeeper in 1764, the Longitude of 

 Barbadoes was 10' 45 /; more to the Westward than the astronomers 

 sent out for the purpose made it. Mr. Kendal's watch made on the 

 same construction as Harrison's, and sent out with Captain Cook (1772 

 to 1775) went much better than Harrison's, but its only fault was 

 " that its rate of going was continually accelerated." 



Mr. Fisher attributes the acceleration to "the magnetic action 

 exerted by the iron of the ship on the inner rim of the balance which 



* Mr. George Fisher, Master of H. M. S. Trent, on the North Polar expedition 

 under Capt. Buchan. 



t The nature of the rock or soil on which the temporary hut for keeping them 

 stood, is not adverted to. We shall presently see that this was of importance. 



