(S7i) 
exceeding great importance, efpccially fince the world now fwanns 
with thofe that are fo very fenfual as to contend, that nothing can 
be underftood but Body. 
In the ficond Book he explains Jirjl the Principles of Ariptle^ 
and difeourfes ac large of the nature and origine of Formes ; yet 
without determining here, whether the Forms of living fubftances 
or the qualities of Bodies are things different froannatter , or nor. 
Next, he treats of the Epicurean Philofophy, as lefs difficult and 
more obvious; difcourfmg of Atoms , their nature and figures of 
continuity , and the manner of the cohaefion of Atoms , as alfo of 
vacuity, &c, 
T&/>^i/, he explains the Qr/^yi^;? Principles; where he hath /fr/? 
a large difcourfe about the nature of dt I^hjJicalBody^ endcavou^mig 
to evince, that theeffenceof ic ccnfiftsnot in a trine Diir.enfion, & ro 
fliew,that the Idea of the three dimenfions, ( than which D^s Cartes 
contends we can have no other of a Body ,)is the Idea only of a Ma- 
thematical, mt a Phyfical Body. Secondly, he treats largj^^ly of 
the Nature and Law of Motion. Ihirdly^ of iheElaftiqueinocions. 
and the caufes of that motion, and of the manners in which it is 
communicated ; as alfo what difference there is in the ccnfi- 
guration of the parts in Springy Bodies, from thofe that have no 
Spring; inquiring alfo, in the Appendix to this Treatife , into the 
efficient caufes of EUfticity, concerning which he delivers the fen- 
timent of Mr. Perrault, after he had alledg'd the Materia fubtilis of 
DeS'Cartes , and the ignited Atoms , and the Iffluvia of Bodies, 
which as fo many wedges do dilate the conftriGed paflTages of the 
inflefled Body. As to the opinion of Mr. Perrault , he fuppofes, 
thatthe ambient Air is of two forts ; thicker, compofed of 
particles of Earth, Water, &c. infpired by us, not pervading glafs 
nor any other Ibl id body ; ihc other, far fubtiler and more pene« 
tranr, intermingled with the thicker, almoft after the manner that 
quick-lime is mixed with fand,both fwimming and moving in the 
£ther , and mixed with it as lime is mingled with water. More- 
over, that as the thicker Air, which extends it felf to fome miles,hath 
its weight , fo the more fubtile hath a greater weight (many Expe- 
riments evincing both.) Now to this fubtile Air Mr. Perrauli 
afcribes the Elaftique power and other affeflions, as the firmnefs 
and cohaefion of Bodies ; forafinuchas thccorpufcles, which ccm- 
pofe every thing} having plainand flat and manifold fuperficies^Sg 
cannon 
