( 10^) 
He refers to bis C^iJ^ef^gr^/'ij' thcfe Difquifitions : whe- 
ther all Comets (in their inniite Motion) move equal Spacet 
in equal Times^ which is the fwifteftj and which the floweft 
Motion they are capable of? what the caufeol this accele- 
ration and retardation of their true Motion ? 
He puts it out of doubt, that they are in the sky it felf, 
producing Reafons^ for it that are very confiderablej and al» 
ledglng among oiher?5 That the P^r^//<«;^f(?/ doe clearly e- 
vince it, which he finds far hfs in Comcts, then in the Hloen^ 
yea then fomethnes in the 5'^^ it felf. Where he'alfo repre- 
fentSj That he hath deduced the Horizontal Far^llax of this 
very Comet from one onely Obfervation, made Febr: ^.ft.n. 
by which he found. That then it was diftant from the Earth 
5000 Semidiameters of the fame, or 4500000 German miles. 
From t hi-s its diftant fromthe earth,he dcduces.That on that 
Day when it was fo remote from the Earthjits true Diameter 
was 2 560 German mileSj which is three times bigger then the 
Diameter of the Earth, and almoft fix limes bigger then 
that of theMooHj whofe Diameterjaccorditig to hisl^^^^f^j 
h^d,7 G:r mm mihs^. 
He finds the MaUer of Comets to be in the ^/i?>e^ it felf^ 
makingthe^tfcrandthe >f;r to differ onely in purity, and 
eftcemjngs That the F/^»e^i do emit their Exhalations^ and 
hsivc their J tmofpheres like unto our Earth. Where be af- 
firmsj That the Sun alone may caft out fo much Matter at 
any time in one Year^ as that thence Qiall be produced not 
one or two Comets, equalling the Moon in Diametetg but 
vtry mjany 5 w^hich if fo^ what contribution may not be 
expcfted from the other Planets ? 
Of this Gomctical Matter^ hethinksj That firft it is by 
Iktle and little gathered togetheXj then coagulated and con • 
cienfcdj and thereby reduced to a lefs Diameter 5 butthen, 
sfter a v.?hile, it refolves agaibj and grows dilute and pale, 
and at laft is diffipated. And accordingly he affirmSj That 
he hath obfcrved the Head of this Comet at firft more con- 
fufcdj thin and pale, afterwards clearer and clearer. 
He 
