Horary Oscillations of the Barometer. 197 
completed five barometers of very different capacities and diame- 
ters, whose difference from the mean and from the standard; with 
all corrections made, was only .006 of an inch. 
Arr. II. On the Alterations of Rate produced in Chrono- 
meters by the influence of Magnetism. By George Har- 
vey, Esq., F.R.S.E., &c. 
Tne power which a magnetic force possesses, of accelerating 
the rate of a time-keeper in some situations, and of retarding it in 
others, is a fact which has been verified by many interesting and 
important experiments. It is singular, however, that the same 
attractive power, which when applied in different directions to one 
‘chronometer, tends either to accelerate or retard its rate, should 
in another, when allowed to operate under the same conditions, as 
to intensity and position, produce results precisely the reverse. It 
will be the object of the following paper, to refer these apparent 
anomalies, to the varieties of imperfect isochronism, existing among 
different chronometers. 
To illustrate this view of the subject, suppose the balance of a 
chronometer in its quiescent position, having its thermometer- 
pieces in an active, but opposite state of polarity ; and let the line 
joining those pieces, and which therefore passes through the centre 
of the balance, denote the direction in which the magnetic force 
acts. Now since the thermometer-pieces possess opposite polari~ 
ties, let that portion of the attractive influence which is destined 
to operate on the time-keeper, and is of an opposite kind to the 
polarity of the thermometer-piece on which it first acts, be allowed 
to exert its energy, the moment the oscillations of the balance take 
place. ‘The effect of such an application will be, a decrease in the 
are of vibration, in consequence of the effort made by the thermo- 
meter-piece, on which the magnetic force acts, to approach the 
attracting pole. This alteration in the amplitude of the are of 
vibration, will therefore occasion some variation of rate in the time- 
keeper. If instead of supposing the attractive power to pass im-~ 
i 
