C 285 ) 
PHILOSOPHICAL 
TRANSACTIONS. 
The CONTENTS. 
An ExtraSt of a Letter fentby DoMor Leibnitz to the Fublijher^ - 
concerning the Frinciple of Exa^neff in the fort Me Watches of 
his Invention, M, Hevelius his Ohfervations of the UJl EcUpfe 
ef the Moon, the Improvement of Corn mWby Sea- [and. ^An 
Accomptof fome Books ; ]. Her metis nMgyptiorum Chemico- 
rum Sapientia ah Hermanni Conringii AnimAdverfiombm vindi* 
cat a per Olaum Borrichium. IT. ihe Garden of Eden, by Sir 
Hugh Plact, nevply reprinted. 
An Extract of a Letter of the Learned Dr.Gothofrediis Gui I.Leib- 
nitz, concerning the Frinciple oj exaffnef in the portable Watches 
of his invention. 
THE Principle I thought upon fome years ago for making 
exaft portable Watches, is altogether different from that 
which confifts in an Equal duration of Unequal vibrations of pen- 
dulums or Springs, applyed to Watches by M. Hugens with fo ge- 
neral an applaufe ; this depending upon a Phyfical Obfervation 3 
but mine being grounded upon a meer Mechanical reflexion, which 
iseafie enough, and whereof the reafonanddemonftration it felf is 
manifeft to our fenfes, which hath not been taken notice of, for 
want of the Arc of Combination, theufe of which is far more ge- 
neral than that of y^^^^r^. For having confider'd with my felf, 
that a Spring being bent to the fame degree,will always unbend it 
felf in the fame time, provided it find the fame freedom of un- 
bending it felf fuddenJy ; I inferred from thence, that there might 
be employ 'd two fucb, one of which ftould play , whilft the firft 
P p Mover 
