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Art. VI . — On the Effects of Magnetism on Chronometers, By 
Peter Lecount, Esq, In a Letter to Dr Brewster. 
S1R3 
JlHE following observations on Chronometers are much at 
your service, if you think them worthy a place in your Journal. 
I find by your last Number, that the subject of the iron in 
ships affecting Chronometers, has employed Mr Barlow’s atten- 
tion as well as my own, and jhat he attributes it to the same 
cause that I do, viz. a portion of fixed magnetism in the steel 
of the balance or its spring. For my part, I think it will not 
be found possible to ascertain any shiprate for chronometers, 
which shall correct the errors arising from this cause, from the 
direction and strength of the attraction of the iron in a ship 
undergoing such considerable changes as it does in different 
dips. I always considered the remedy to lie alone in the hands 
of the maker, who should carefully ascertain that no steel what- 
ever in a chronometer possesses any fixed magnetic quality ; 
and I pointed this out to a chronometer-maker in London, in 
November 1820, shelving him, amongst a number of balances, 
those which had any portion of fixed magnetism, and those 
which had not, &c. ; but it is requisite, that, in this respect, not 
only the balance and its spring should be attended to, but that 
all the steel in the instrument should be deprived of this qua- 
lity, particularly the steel-spindles of the fusee, barrel, &c., for 
it is to magnetic attraction, residing wholly in the machine, that 
I attribute the alteration which takes place in the rates of chro- 
nometers on shore in different parts of the world, and which is 
often very considerable. These attractions may act in several 
ways ; if there is fixed magnetism in the balance, and variable 
magnetism in the spindles of the wheels, the rate may be alter- 
ed by any considerable alteration in the dip, as the direction 
and strength of the variable magnetism will thereby become 
changed ; the same effect may be produced, if the fixed mag- 
• Mr Lecount is already known to the public by his interesting work “ On 
the Changeable Magnetic Properties possessed by all Iron Bodies, and the diffe., 
rent effects produced by the same on ships’ compasses, from the position of the 
ship’s head being altered,” Lond. 1820. Some account of his Observations will 
be found in this Journal^ VoL IV., p. 296., &c, and p. 436.«-E». 
