384 Mr Barlow on the Effects 'produced on the Rates of 
Royal Military Academy, this removal having been rendered 
necessary, in consequence of Mr Evans retiring from Wool- 
wich. 
Each watch remained in its place three or four days* and was 
then removed to a different situation to the east, west, north 
and south ; the direction in which each watch was placed, was 
also carefully observed ; the twelve o'clock mark first pointing 
to the north, then to the east, west, &c., and a very considerable 
difference was observed accordingly ; and as often as any previ- 
ous situation was resumed, the watch was always found to re- 
turn to the same rate ; and the greatest care seems to have been 
taken to remove every thing of a magnetic nature front the 
place of observation, in order to be assured, that the effect pro- 
duced should be due to the action of the iron only ; and which, 
in his former experiments, Mr Barlow had ascertained to be 
perfectly free from any portion of fixed magnetism. 
The effects produced, which, in some instances, amounted to 
about 5" per day, must, therefore, be due to some magnetic pro- 
perty in the balance or spring of the chronometer ; and to be 
satisfied on this point, Mr Frodsham, of the firm of Gaskinson 
and Frodsham, whose chronometers were so highly distinguish- 
ed in the late voyage to the north, went down to Woolwich 
with detached balances and springs removed from chronometers, 
for the purpose of experimenting upon them ; and the results 
perfectly satisfied both parties of the truth of the above conclusion. 
Perhaps the very nature and office of the balance-spring, is that 
which is the most likely to communicate to it a fixed polarity, 
and which, of course, will be immediately communicated to the 
balance, however free from such action those important parts of 
the machine may be, when first delivered from the hands of the 
maker. It being, then, almost impossible to prevent the acquisi-* 
tion of magnetism by the balance, it becomes important to esti- 
mate its effects ; and hence the utility of such experiments as 
those above referred to, is sufficiently obvious. 
In his former experiments, Mr Barlow made the singular 
discovery, that the power exerted by iron on the compass needle, 
resided wholly on its surface , and was independent of the mass ; 
the same, it was easy to conceive, would be found to be the 
case with its action on chronometers, and a very few experiments 
