1851.] On the Rates of Chronometers, 63 



is made of steel," and he made several experiments upon Chronometers 

 with magnets, to confirm his views. 



In 1821, Professor Barlow, at Woolwich, made a very complete series 

 of experiments, shewing that the vicinity of masses of unmagnetised 

 iron invariably affected the rates of Chronometers placed [near them ; 

 and he rightly suggests that such variation can only be supposed to 

 arise when the balance has acquired some polarity ; but it is curious 

 to find that Professor Barlow was evidently not acquainted with Mr. 

 Varley's paper as quoted above, which had exactly proved so long 

 before what he so acutely conjectures ! He even goes on to propose 

 Mr. Varley's experiments on a detached balance, but does not make it ! 



Professor Barlow's paper appeared in the Philosophical Transactions 

 for 1821, and a resume of it is given in his celebrated Essay on Mag- 

 netic attractions of which the second edition, now before me, was pub- 

 lished in 1823.* Lt. W. Mudge in the Edin. Phil. Journal for 1821, 

 p. 381, describing the peculiar magnetic deviations found on Mayo 

 and the Great Salvage, as also an instance where the compasses of a 

 Hudson's Bay Company's vessel became suddenly affected at sea in 62° 

 N. ; 93° West ; relates also that one of the surveying party on the 

 Great Salvage having laid down his watch on the rock in the morning, 

 found when he took it up again, in the afternoon, on his return to the 

 same spot, that it had gained two hours in the interval " an acceleration 

 doubtless due to the action of the magnetic rock on the balance." In 

 our Journal, Vol. XVIII. p. 410, will be found Capt. Campbell's 

 account of a very remarkable local deviation of the compass at Saugor 

 in Bundlecund, by which a boulder of magnetic Diorite rock was found 

 buried in the earth when dug for at my suggestion, with my remarks. 



In the Nautical Magazine for 1837, Mr. Fisher, adverting to a 



* Professor Barlow states, p. 126, " that a Master in the Navy to whom he had 

 described his experiments told him that, when master of a first rate, he found that 

 his Chronometer ' which was an excellent one invariably altered its rate 5' when 

 taken on board, but that he could now account for the difference, recollecting that 

 he had placed his Chronometer nearly in contact with an iron knee." The same 

 perplexing fact occurred to myself with a fine box Chronometer in 1817. In the 

 Nautical Magazine for 1845, an instance is given by Captain Wise of the City of 

 Berry in which an error of 90 miles between Java Head and Cape Lagullas occurred 

 with an excellent Chronometer near to which a pair of pistols had been placed ! 



