198 Le Roy’s Memoir on the best Method 
mountable, or experienced a considerable friction of the parte 
one against the other; whence it is evident, that, a suspension 
spring being necessarily much more extensive in its width 
than a wire in its size, it can but be very long, and conse- 
quently very embarrassing. Independently of the defects 
which we have before remarked in it, the necessity of using 
a very fine suspension wire (by having recourse to the means 
which [ used to place this wire out of the way of accidents, 
to which its fineness exposes it) is therefore proved. (See 
Article VIII. Part [1,) 
Observation ITT. 
On the substance of the regulator. 
/ 
Steel appears to me preferable to construct the balance of; 
being a snbstance less dilatable, more solid, and Jess variable 
by the eficet of ieat, than brass, &e. The fears of magnetic 
influence are not, in my opinion, of any consequence. For 
them to have any foundation it would be necessary for this 
balance to acquire poles, which can never happen in a body 
that is continually changing its position; every effect which 
only increases its weight, or gives to its mass a tendency to- 
wardssone side, wou!d produce nothing in the vibrations, 
the balance only acting by its inertia, 
Observation IV. 
On the motion of the balance. 
The friction on the pivots of the rollers which contain the 
balance of the new watch is almost nothing; for the follow- 
ing reason: The pivots of these rollers have necessarily a 
Nittle play in their holes; whence it happens that, when 
these rollers describe a very small arc, their pivots only rest 
on the edges of their holes without rubbing. To receive 
the full adyantage of this, and to have besides more free- 
dom, .a less resistance on the part of the air, &c., I have 
only rendered the arcs of. vibration as great as the effect of 
shocks appeared to me requisite to be prevented. Each vi- 
bration of the balance is half a second, and the watch beats 
seconds; this appeared to me the most convenient and the 
jnost advantageous, I could not have increased the number 
of 
