( 5 ) 
but better calculated for adhefion. Thefe 
form the grofler bodies. 
Sol et Fixte are compofed of the firft ele- 
ment; Ccelum of the firft and fecond; opake 
bodies, fuch as comets and planets, of the 
third. 
According to this philofopher, rarefaction 
is caufed by the introduction of celeftial 
matter into the pores of denfer bodies : caufa 
ordinaria, he fays, ignis eft, quia cum particulte 
materia fubtilis^ quibus conftat, in continue fint 
motUj facile aliorum corporum meatus ingredi- 
untur atque illos 'dilatant et extendunt. 
Gravitation he explains thus: Denfe bo- 
dies having lefs propeftfity to fly from the 
centre round which they are whirled, remain 
neareft that centre, where they are con- 
ftantly prefied by the more fubtile elements. 
In anfwer to the objection, that, according 
to this hypothefis, bodies falling to the Earth 
fhould defcend with mofll- rapidity at firfr, 
pafling then through the thineft medium, 
he fays Di'verfttatem lapidis inde oriri y quod 
lapidis, infuo defeenfu y motm precedents et in- 
Juper augment urn recepit y ab impulfu materite 
fubtilis. 
In fpeaking of compound motion, he fays, 
> Omnia 
