of measuring Time at Sea: 145 
points of suspension which feel it, and that the lower part 
of the pendulum, or the watch, remains almost fixed at that 
moment; this pendulum then redescends by an inclined 
plane to the vertical, whence it was removed by the shock, 
and that by a gentle motion, progressive and slow, which 
can neither affect nor derange that of the spiral springs. 
These motions, although rendered more gentle and infi- 
nitely less prejudicial, nevertheless cannot be otherwise than 
contrary to the accuracy of the watch, if they were of long 
duration ; that is to say, if the oscillations of this watch, 
forming a pendulum, continued like that of the common 
pendulums: this construction would then have had another 
more considerable disadvantage. These oscillations would in- 
crease by a continuation of shocks ; whence it would happen 
that the points of suspension would be worn; that the watch 
would be found, in a great number of instances, in situations 
very remote from the vertical (which is the most advantageous 
Situation, being the one in which it was regulated); and that 
the sum of the motions, now rendered less conttary to trath, 
would he considerably augmented. I have prevented this 
inconvenience, Ist, by gentle friction springs acting near 
the points of suspension on planes or large surfaces; which, 
with a sufficient resistance to diminish considerably the oscil- 
latory motion, are very little subject to wear, and neverthe- 
less permit the watch to move on thcse axes: @dly, by a 
pad B, B, (fig. 2. Plate 1V.) formed at the bottom of the 
case which contains the watch, and by cushions which are 
placed round the sides of the box, in such a way, that in 
great shocks the lower part of the watch meets obstacles 
that are supple and moveable, which extinguish the motion 
by their softness, and prevent it from continuing. 
But a very essential point to render the motion of the ba- 
Jance unalterable by shocks is, as M. Bernoulli recommends, 
p- 39, of the Researches above cited, that it be of equal 
weight throughout. This is one of the considerations which 
has induced me to use two opposite spiral springs in my 
watch *, both opening and shutting together, in order that 
* Sully used two spiral springs in his watch. See the Description alregée, 
p- 175 and 177.1. S. E. 
Vol. 26. No. 102, Nov. 1806. K each 
