of measuring Time al Sea. 143 
agitations of all the parts of the machine, especially those of 
the regulator, the situation, the form, and the texture of 
these parts may be changed; whence arise errors so much 
the more important, because, instead of being transitory, as 
others are, they would only cease when we had applied the 
remedy to the changes as they happen. 
The methods which appeared to me proper to prevent 
these inconveniences are, Ist, to render all the parts of the 
watch.as solid and as unalterable as they can be made: 2dly, 
to suspend the machine in such a way that it may receive 
little motion from shocks: 2dly, to diminish the effect of 
this motion as much as it can be done: lastly, to arrange 
things in such a manner, that this motion when received — 
may not be preserved, but may cease, on the contrary, as 
soon as possible. To fulfil these different conditions, [ took 
care not to give my spiral springs too great a magnitude or 
mass with regard to their strength. M. Daniel Bernoulli 
recommends in his Mémoire to make them very large; but, 
having applied some of them to my watch, I presently per- 
ceived that agitations a little considerable made them move 
and yibrate not only according to their length, but even in 
their width; whence I concluded that there was a mean 
term to be chosen in the size of these springs. After some 
experience, I fell upon that point of magnitude in the spring - 
where all the vibrations are exactly isochronous* without 
being affected by considerable shocks. 
Nothing could appear more opposite to that solidity, which 
isso necessary in the parts of the regulator, than the harpsi- 
chord wire by which itis suspended. Although its strength 
be such as to sustain a weight fourteen times greater than 
the balance without breaking, nevertheless it was much to 
be feared that it would not withstand violent shocks (which 
happened, in effect, before | bad taken the precautions which 
Tam going to mention), or at Jeast that it would lengthen. 
To prevent this inconvenience, J attached the upper extre- 
mity of this wire toa spring x,x (fig. 7. Plate I.), sufficiently 
strong to keep the wire and the balance suspended, and ele- 
Vate it to a fixed point above, against which this spring 
presses, ands stopped ;-by this means it is no longer the 
* See Article I. of Part Il. . 
wire 
