202 Le Roy’s Memoir on the best Method 
as we have explained in ihe Second Part, in the non-isochro~ 
nism of the vibrations of the regulator; 2dly, in its little 
power and freedom; 3dly, in the multiplicity of friction 
which it experiences ; 4thly, in the variations to which it is 
subject by heat and cold; Sthly, in the bad effect of shocks. 
Now it is, I believe, demonstrated in the Third Part, that 
the method which [ have found to give the balance a perfect 
isochronism by the length of the spiral spring * is incontesta- 
bly the most simple, the most certain, and the most exact. 
2dly, That it is not possible to render the regulator more 
powerful, more free, and more disengaged from friction t, 
than I have made it by my suspension, my escapement, the 
double spiral spring, the rollers, the moveable pieces, the 
situation of the balance, its size, &c.; which is proved by 
the experiment related in Article V.{ 3dly, That the me- 
thod 1 have used to correct the effect of heat §, which is 
‘not subject to the inconvenience of giving way like me- 
tallic compensators, which are made securely and without 
play, which leave the Jength of the spiral spring constant, 
and do not destroy the isochronism of its vibrations, &c. is 
incontestably the best. 
4thly, That the methods recommended Art. VIT. Part III. |] 
to correct in a marine watch the effects that heat leaves after 
it, that is to say, the gain or loss which sometimes follows, 
are probably the most efficacious. 5thly, That the expe- 
dients to which I have had recourse to render the motions 
impressed by shocks less abrupt, of less magnitude, and less 
durable, are, without contradiction, the most certain, and 
likewise those which I have used to regulate the watch to 
the smallest quantity **, without changing the length of the 
spiral spring, or destroying the isochronism of its vibrations, 
All these methods, therefore, appearing to me indisputa- 
bly the most certain, the most simple, and the best that can 
be used to perfect the watch, I have some hopes of having, 
conformably to the demands of the Academy, determined the 
lest method of measuring time at sea. 
* See page 61 of this volume. + Page 60. + Page 131. 
§ Page 138, || Page 141. 4] Article VIII. Part III, p. 142. 
** Article VI, Part IL p. 137. 
APPEN« 
