( $0B2 ) 
much ncgleded indudion. Where he takes occafion to fpeakofan^l 
commend that way of finding oat the Efficient caufes of things, cali'd 
by the newly raention'd Lord InHmU Cruets^ becaufe, like a Crofs 
creded where more ways than one do meet, it (hews which of them 
you are to take. Which, among others, be illuftrates by ttie example 
concerning the Queftion of the Canfe of Gravity, viz,. Whether it be a 
Quality inherent in bodies,or the Magnetical power of the Earth, or 
the Circum-ambient Air or >£ther f Alledging for this purpofe an 
Experiment, Teeming to him to be fuch a determining inftance as hath 
been fpoken of made by Monfieur Hugens before the Royal Acade- 
my at ?a.rls^ and related at large by Monf. Rohault in his Traite de 
Phyftque^ printed 2.1 Paris A, i6yi,part:Z, ch. 28. p. I22% to which wc 
refer the Reader \ baftning to 
The Fourth and lafl: part or this Book, which confiders the Powers, 
Nature, and Immortality of the Rational Soul, and is follicitoufly 
employ'd in folving many difficulties occurring about this matter : 
Which being a fubjeA not fo proper to the defign of thcfe Trads, we 
fiiall here forbear to enlarge upon. 
V. A Lm^t France fco Redi concerning fome Objedions made 
upon his Obfervations about rZ/j^-ry ^ together with a Reply to that 
Letter by M&yfe Charas : Now both Printed in Englijh Sor John Mar- 
tyn. Printer to the R.Society,at the i?^// in Pauls Chnrchyardyitjz, 
in 80 •, and formerly defcribed in thefe Tracts^ viz. Numb, 66. f 20^6. 
and Numl^ 3 • P» 4^7 3 ♦ 
VL De Gemmarum Origine & ViribHs Exercitatio : Autb. Roberto 
B^yle, Nobili Anglo. This Trad was alfo formerly, when it flrft came 
abroad in E?zj;/^/^, defcribed, viz, in iV^w^. 84. p. 4095. and is now 
mentioned again, only to give notice to Forrainers, that *tis printed 
in Z^^i/? for the fame Bookfeller, for whom was printed the Englifh 
Edition. 
Errata h this TraEi-. 
Pag. 50^3. 1. 19. r,tnitsfrifiine. p. 5055. \,26. r. 'vehicle. 
LONDON, 
Frintedfor loXmlAAiVja, Printer to the J^oyal Society ^ l6jt. 
