( 2012 ) 
:^3«A11 thefe Rules are true, whether the bodies be e^ual or 
unequal. 
24. A body movtth m pleffo as freely as in vacuo. 
25. ThePercuffionsote^«<i/ bodies are made in pleffa asin 
t/^<:«i?.Butwhen the bodies are uneqnal^ the Percuffions 
^re made in pleno otherwfle than in vacuo^ 
a6-The Percuflions of unequal bodies cannot be reduced to 
one General Rule. 
aj.Of Refraction. 
28 An Appendix containing a Review of this Di cour(e> 
\yXongieftnrePhjficO'Ajironomkhedella Natnra clelVni^ 
z/er/^3<^^ Pietro il</«Cavina 5 inFaetiza^ 1663;. 4*. 
THefe Conjeftures are raifed by the Author upon fome 
Celeftial obfervations about the fixed Stars at Faen^^, 
The vvhole Traft confifts of three parts ^ Confidtra ions, 
^Obfervations^and Reflexions. 
In they?3;y25this Writer taketh notice, i. That men for many 
Ages have lb much doted iipon Arijioik.^s to deny Faith to 
Senie^and Proof to Experience* ?.That one of the received, 
and much contended forj Arifiotelian opinions is that of the 
Ingemrahiliiy and Incorrnpihiluy of the Celeftial Bodies^but 
that Heaven it felf,impatient,as *twere,to befo little known, 
hath generated Nezi? Stars 3 brighter than the known ones 5 
thereby to ftrike the eyes of men, that are curious and dili- 
gent in the inveftigatian of truths. And hence he proceeds to 
fhe 
Second part ^ containing the Ohjervatiofjs themfclves , 
whereby he affirms to have found confiderable changes in 
divers of the F/jve^ Stars from yN\i'At Bayer us 2ir\a others have 
remarked of themjSS^to Magnitude and Number^inftancing 
in Vrja both Minor and Majcr^ in the Dragon^ Cefens^ Bootes^ 
Corona Septentrionalis^HercHlesyLyra^Cygnffs^CaJJw^^ 
and the Via LaSea* 
Whefeupoh in the third part,having premifed his method 
^ofobfervingand Meafuringj he maketh thek Refieffions 
