^50 
;jof /making. .the vibrations of the .balance isochronous by the 
?.nature of i the . spiral, the artist would be obliged to submit to 
Dali i the trouble and care required in the-execution of the escape- 
ment with; a constant, force. 
' The. free; , .escapement of Ear nshaw is at present the one 
chiefly used in the construction of chronometers for navigation, 
as- it. produces a great regularity, and is not very diflicult in the 
• execution. .It is preferable to Arnold’s, from having less fric- 
tion, being less liable to be stopped, and being less difficult in 
the construction. Its superiority is proved by its being employ- 
ed by; the best artists, and by the British Government having 
..awarded L. 3000 to Mr Earnshaw for its invention. 
; The means used by Mr Earnshaw to diminish the friction of 
4 his: escapement, consists, 
1st, In giving a greater diameter to the circle of escapement, 
which causes the CvScapement- wheel to act by a longer lever, and 
^more perpendicularly against the line of centres. The push thus 
becomes shorter and more gentle, and operates with less play, 
and consequently with less friction. - 
r^dlv^ In supporting the detent at the extremity of the teeth 
.-6f the . escapement-wheel, by which disposition, the pressure, of 
,.the, teeth of the .wheel against the detent acts by the longest pos- 
sible radius, consequently with less pressure than in the escape- 
..ment, of Arnold, and thus the regulator also has less friction in 
; disengaging the detent. A chronometer with an escapement of 
Earnshaw’s, admits a balance both greater and heavier than one 
with an escapement of Arnold’s, and, therefore, there will be a 
X greater quantity of motion with the same moving power, an 
.evident proof of a reduction of friction. 
Notwithstanding these advantages, the ‘author of this paper 
conceives, that the diminution of friction in that escapement may 
be carried much farther ; and a model on a large scale, executed 
. with that, intention, proves that this advantage is obtained with- 
fOUt any inconvenience. It would be tedious to describe in de- 
'tail this escapement, which could only be made intelligible by 
41 plan both of the front and side of it ; but for those who are ac- 
.quainted with the; escapement of Earnshaw, it will be sufficient 
;to. say, that instead of one escapement wheel he employs two 
upon the same .axis. One of these acts by impulse on the es- 
^{jiJCfpement circle, of which the diameter is in a still greater ratio 
