Chap. 7. A Trettift of B O D I E S. 



fewell and is grown maPccr of it by introducing into it fb ma- 

 ny of its own parts, ( like fb many fouldicrs, into an enemies 

 town ) they break out again on every fide with as much vio- 

 lence as they came in. For by reafon of the former refiftancc of 

 thefcwcll; their continuall ftreaming of new parts upon it, 

 and one overtaking another there where their journey was 

 flopped, ( all which is encreafed by the blowing ) doth fb ex- 

 ceedingly condenfc them into a narrower room then their na- 

 ture afrc6teth, that as foon as they get liberty, and grow ma- 

 flers of the fewell, ( which at the nrft was their prifon) they 

 enlarge their place, and confcqucntly come out and flie abroad; 

 ever ayming right forwards from the point where they be- 

 gin their journey : for the violence wherewith they feck to ex- 

 tend themfelves into a larger room, when they have liberty to 

 do fo; will admit no motion but the fhorteft, which is, by a 

 ftraight line. 



So that if in our phantafic.we frame an image of a round bo- 

 dy all of fire; we mutt withal! prefently conceive, that the 

 flame proceeding from it, would diffufe it fclf every way in- 

 differently in ftraight lines; in fuch fort, that the fburce ferving 

 for the center, there would be round about it an huge fphere of 

 fire and of light; unlcfTe fome accidcmall and extern caufe 

 fhould determine its motion more to one part then to ano- 

 ther. Which compafie , becaufe it is round, and hath the fi- 

 gure of a fphere, is by Philofophers termed the fphere of its 

 activity. 



So that it i's evident, that the moft fimple and primary moti- 

 on offircjsa flux in a direct line from the center of hr, to its cir- 

 cumference, taking the fewell for its center; asalfo, that when, 

 it is beaten agiintf a harder body, it may be able to deftroy it, 

 although that body be in its OWH nature more denfe then fire. 

 For the body againft which it prcflech, either hath pores, or 

 hath none, ( as, the Elements have none : ) if it hath pores ; 

 then the fire, by reafon of the violent motion of the impellent:, 

 driveth out the little bodies which fill up thofe pores, and fuc- 

 ceeding in their room, arid being multiplyed there, caulech thofe 

 effects which in our difcourfe of the Elements we affigned to 

 heat. But if it have no pores ; it will be either rare or denfe : 

 if it be rare; then, in cafe that the force of the impellent be 



greater 



