On Sal Nitrinn and Nitro- Aerial Spirit 65 



particles and the subtle matter existing in the interior 

 cannot as in other cases extricate themselves. Hence 

 it is that in glass contracted in this way the subtle 

 matter imprisoned among the minutest particles of 

 the glass has not room as before for freely continuing 

 its movements. For resistance is made to the move- 

 ment of the subtle matter, from two causes ; first, 

 because the particles of the glass being at rest do not 

 yield to the movement of the subtle matter as before ; 

 and secondly, because the particles of the glass in sub- 

 siding under the pressure of the atmosphere are driven 

 into the little spaces in which the perpetually agitated 

 matter carries out its motion. Hence that matter 

 strikes the particles of glass which oppose its motion 

 and endeavours to part them from each other. Indeed 

 the case is very much as if the glass were bent almost 

 to breaking ; in fact it is to be observed that the 

 pulsation of the subtle matter is almost capable of 

 breaking the said glasses, as is evident from the fact 

 that when drops of molten glass are dropped into 

 water most of them immediately burst asunder ; and 

 indeed we must suppose that all the rest just escape 

 being broken. 



Wherefore when the beak of this kind of glass is 

 broken, the force of the subtle matter, aided somewhat 

 by the concussion of the whole glass caused by the 

 fracture of the beak, is now able to draw the particles 

 of the glass apart and to thrust them out with violence. 

 I add further that when the glass is broken in any 

 part, the particles of glass which were previously con- 

 fined by its extremely solid surface, rush out by the 

 open door at the very moment when the effort of the 

 subtle matter begins to take effect, and by this no 

 small addition is made to its force. And, finally, let us 

 further consider that the pointed beak of the glass 



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