,( iji8 ) 
infeft it with qualities pernicious to the temperament of our 
Vegetables and Animals 3 and from thence may arife all thofe 
effe(fts,.^which by long obfervations and common confent ot 
^Mankinds have been attributed to Comets, notvvithftanding 
of their being ridiculed byfome Modern Philofophers. From 
this he pafles to fhow, the method by which the Orbits 
the Comets are to be detcroiined. The ways , he takes, are 
not only excellent in that cafe, but likewife of great ufe in 
iblving other intricate and difficult Problems in Natural Phi- 
lofbphy. And then he gives the way of finding both the 
Heliocentrick andGeocentrick places of a Comet tor any given 
time, /and defcribes Tables that are neceflary for the more 
ready performance of it. 
The 6th and laft Book is upon comparative Aftronomy 
where he confiders the Ph£nofMena that would appear to a, 
Spectator placed in each of the Heavenly Bodies, and com- 
pares them with thofe that are feen trom the Earth.The chief 
of thofe he takes notice of are their viciflitude and duration 
of Days and Nights, the apparent Bignefs, intenfnefsof Heat, 
and light of the Sun, the length of their Years, and variety 
of Seatbns, the phafes of the Moon, and the Eclipfesof the 
Luminaries, the Number, Diredions, Stations and Retrograda- 
tions of the Planets that are to be feen,and the helps they may 
afford to difcover the true Syftem of the tiniverfe. After ha. 
ving given usan account of all fhiefe appearances in each'ofthe 
Heavenly Bodies, he (hows us that of ail rhe Primary Planets, 
the Earth is the fitteft place where an obferver may difcover 
the true Syftem of the Wsorld, and Mercury the raoft unfit 
for that purpofe 5 and that therefore an Inhabitant in any 
one of the Planets, may upon better reafons fuppofe his own 
Habitau9n imiriGveable, and that the whole Heav(:ns turn 
round about him ^ - then thefe which our Terreftri il ob- 
fervers have for their immobility, and having tcv/er argu- 
ments, it will be harder to convince them ot their own mo- 
tion. We may rcafonably then imagine, that an Arftonome 
in any of the other Planets^ as for example in Venns,^ would 
(iipgofc his [^wnj Habitation immoveable , and would 
7 . endea^ 
