198 Mr. Harvey on the influence of 
mediately through the thermometer-pieges, it be allowed to pro- 
duce its effects, on either side the point of quiescence, within cer- 
tain limits, the are of vibration will still be diminished, but in a 
less ratio than before; and changes of rate proportional to the 
variation of amplitude, will be the result. 
Suppose in the next place, the direction of the magnetic force to 
pass through the centre of the balance, and the limit of the semi- 
are of vibration; it is manifest, when motion is communicated to 
the balance, its effect will be to increase the arc of vibration, both 
from its attracting one of the thermometer-pieces, and repelling 
the other; and that therefore an alteration of rate, entirely the 
reverse of the former, will be the necessary result. It is also evident, 
that if the same attracting pole be applied on either side of its last- 
mentioned position, within certain limits, the are of vibration will 
still be increased, but in a less ratio than before; and alterations 
of rate of the same kind, but of a less remarkable degree, will be 
produced. 
If the time-screws are supposed to be magnetic, and the ther- 
mometer-pieces free from the attractive influence, similar results 
will take place. 
Conceive in the next place, that in addition to the magnetism of 
the thermometer-pieces, the entire arcs of compensation possess 
also a property of the same kind ; one half of each having northern 
polarity, and the other half southern; then will the time-screw 
attached to the are of compensation, whose thermometer-piece has 
northern polarity, become a south pole; and that attached to the 
arc, whose thermometer-piece has southern polarity, a north pole; 
the transverse arm connecting the two, if of steel, presenting all 
the properties of a perfect magnet. 
In this point of view, the entire balance may be regarded as a 
species of compound magnet, having two pair of opposite poles ; 
and different phenomena will be exhibited, according to the direc- 
tion in which the magnetic force acts. If, for example, the mag- 
netic power be allowed to develop its influence, in a direction 
equally remote from the opposite poles of each of the arcs of com- 
pensation; and that we moreover suppose each pole to possess the 
