M.BeS'CArtci to that late Noble and Learned Englifli Knight,^ 
Sir Charles Cavendilh. The other is , whether Motion can be 
made without fuppofing a where 'tis reprefented , That^ 
if one comprehend well the Nature, afcribed loth^ Materia fub- 
tilis^ and how Motions, called C/>i;»/4r 5 are made, which need- 
not be juft Ovals ox true Circles , but are only called Circular, in 
regard that their Motion ends, where it had begun , whatever 
irregularity there be in the Middle 5 and alfo, that all the Ine- 
qualities, that may be in the Magnitude or Figure of the parts, 
may be- compenfated by other inequalities , met with in their 
Swiftnefs , and by the facility , with which the parts of the 
Subtle alter , or of the firft Cartefian Element , which are found 
every where , happen to be divided , or to accommodate their 
Figure to the Space, they are to fill up : If thefe things be well 
underftbod and confidered,that then no difficulty can remain touch- 
ing the Motion of the parts of Matter i;? flem, 
Befides all thefe particulars , treated of in this Tome^ there oc- 
cur many pretty Queftions concerning Numhers , the Cycloid y 
the manner of Working Glajfes for Telefcofes , the way of 
Weighing Air , , "and many other Curiofities , Mathematical and 
Ehyfical, 
//. ASTRONOMIA REFORMATA , Juctore 
JGHANNE BAPT, KICCIOLI , Soc. 
Forthe Notice of this Book ^ and the Account of the Chief 
Heads contained therein , we are obliged to the journal des Sea- 
vans t, which informs us^ 
Firft , That the Defign of this Work is , that , becaufe fevc- 
ral Aflronomers^ having had their feveral Hjpothefes^ there is found 
fo great adiverfity of opinions, that it is difficult thence to con- 
clude any thing certain 5 this Author judged it alfoneceffary, to 
compare together all the beft Obfervations , and upon examinati- 
on of what they have moft certain in them , to reform upon that 
meafure the Pnnciples of Jftronomy. 
Secondly^ That this r^///^^^ is divided into two Parts ^ where- 
of the Fn(l.- is compofed of Ten Books 3 in which the Author 
confi» 
