142 Le Roy’s Memoir on the best Method 
wire which sustains the balance in great shocks. Then, the 
suspension spring, which could only raise a weight a little 
greater than the balance, gives way, and the extremity of 
the lower pivot of the balance touches and rubs during the 
mometit of the shock on a plate, as is done in common 
watches when they are laid down. 
An essential thing to determine was the magnitude of the 
vibrations, 1 acknowledge that the true place where we 
might find this with most success would be a sea-port. 
M. Bernoulli recommends that they should be very small ; 
but I feared then that shocks would have had a considerabie 
effect on them. I have therefore made the balance describe 
an arc of about 100 degrees in the long vibrations—that is 
to say, when the watch is just wound up—which is reduced © 
to 90 after the watch has been going 24 hours. In other 
respects I have followed the principles of M. Bernoulli, zdid. 
who requires that a considerable motion of the balance should 
produce little change in the fignre of the spring. 
After having put the regulator, by the proper disposition 
of its parts, as much as possible out of the power of shocks, 
to fulfil our views entirely, it is necessary to find some me- 
thod of rendering these motions as small as they ean be; 
the Jeast abrupt, and of as short duration as possible: this 
is what I have done by the suspension which I have given 
to the new watch. 
The motions which it may receive can only be either ho- 
rizontal, vertical, or m a direction compounded of these 
two. To compensate the first, which would particularly | 
affect the spiral springs, I have suspended and rendered my 
watch moveable on two axes A, A (fig. 1. Plate [V.) adapted 
to a frame or strong parallelogram of copper AB, AB, which 
itself, as well as the watch, turns on two other axes BB, 
fixed to the box, which contains the whole maghine*. By 
this means the watch forms a kind of pendulum, at the bot- 
tom of which are placed the spiral springs. When, there- 
fore, they receive a shock, we see at first sight that it is the 
* A watch suspended in this way is said to be hung upon ‘gimbals. Ber- 
fhoud (Eclaircissemens, p. 53.) attributes the contrivance to Cardan: but I 
hawe seen an old work on Mechanics, of much earlier date than ‘any thing of 
Cardan’s, where this suspension was proposed for a carriage to convey 
wounded soldiers from thetield of battle, or from one place to another.—T.S.E, 
points 
