Mr. Bond on the Comparative Rates of Chronometers. 85 
by Arnold, lost about 9” by removal from the vessel to the shore, 
and another by Pennington still more. The variation in the shore 
rates is also remarkable, that of the first appearing to have 
been 8”, of the second 6.14, of the third 7.2, and of the fourth 
8”. All these errors were noted during the short period of 
seventeen days. 
It is evident, that either the instruments used in these exper- 
iments were not well adjusted, or that some extraordinary cause 
operated to produce the effect described. Mr. Fisher was of 
opinion that this acceleration arose entirely from the magnetic 
action exerted by the iron in the ship on the inner rim of the 
balance of the Chronometer, which is made of steel; that the 
iron in the ship forms “altogether one large magnet, having its 
south pole, on deck, nearly amidships, and its north pole below ;” 
and all his subsequent experiments were made on the supposi- 
tion that the magnetism was fixed. It is, however, well known, 
that a bar of iron, in the state in which it commonly occurs, will 
affect the magnetic needle very differently when placed in 
different positions as it regards the magnetic equator. Hence 
if the balance is to be considered as a nicely suspended 
magnet, it would follow that every different inclination of the 
vessel would produce a corresponding change of rate. 
It is better in the first place to ascertain from direct experi- 
ment whether Chronometers have or have not any systematic 
variation, dependent on their being placed on ship-board. The 
tables of the change of rates of Chronometers furnished by Mr. 
George Coleman, which accompany Mr. Fisher’s communication, 
go a great way toward reducing the excessive errors which 
were thought to exist; but these are generally defective in 
not giving the subsequent shore rates, as there are many 
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