( 28.7 ) ^ ■■ 
delivers them by a reciprocal good office, md renders to the 
Spring M the fame fervkes, which it had received fTOmsit, with 
an expe'flation of receiving the like again. 
Which being well confidery , ^tis manifeft, tf^a the fame alter- 
native Motions will continue always: fha the periods taken 
from the very niomenc that one Spring begins to unbend , una! 
the niomenc it once unbends it feJf again, wjU always be of e- 
qual duration,, though the two fmall Springs be not equally 
ftrong: that tht Bailance of fuch a Watch will be double, and 
be charged more or lefs , and receive delay , by advan- 
cing or recoiling, aiong the two arms, two equal vveighcsj 
^counter-balancing one another, that fo the change of the fcituati- 
on may not at all prejudice the Equality of the Watch. For the 
reft, we may in this kind of Watchesfparethe fufee, and confe- 
quently the ftringor chain. 'Tis alfo eafic to judge, that fuch 
Vi^atches as thefemay be of a fize fufficiently fmall ; that they will 
make no more noife then ordinary Watches ; that they will be as 
exaftas pendulums, and ceafe not to go whilft they are vvinditig 
up. ^ And though the motion of the Watch-wheels may be altered 
by many accidents, fuch as are, the inequality of the motion of 
the great ordinary Spring, I mean, the firft Mover ; the more or 
lefs rubbing of the wheels according as the oyl grows thiijinejr or 
thicker^ the ruft, the verdigreafe^ the play of the pieces, the 
inequality of the teeth, and the like ; yet the periods of the 
fiiiall Springs will not be concern din all or any of them, provi- 
ded the motion of the Watch-wheelshave always more ftrength 
than it needs to bend them again; which is in our power. Andfo 
the Principle of Equality here is fure by a kind of demanftiSHon 
altogether Geometrical, and withal very evident even to ordinary 
capacities. 
ft remains to touch in a few words the objeftions that have 
been made againft this contrivance by fome intelligent perfonst 
They have all acknowledged, that this would be a perfeftly ex- 
aft Watch for common ufe , but if employed for finding the Lon- 
gitudes, there would occurr thefe difficulties, viz. That toffing 
of Ships would fliake the Springs as well as other pieces ; that ru/t 
would fpoilthem, fince thefaltifh humidity of the Sea in remote 
voyages fpares not the veey needles of CompalTes though inclo- 
fed in boxes ^ that the changes of feafons and climats will fenfi- 
bly alter the Springs, efpecially the great heats , or rains within 
Pp 2 the 
