86 Mayow 



that aerial particles are altered in some way by the 

 breathing of an animal or the burning of a lamp, and 

 that they contract in consequence into less space, as 

 was previously said. 



From this it appears to be established that aerial 

 particles are not fit to sustain fire and life unless they 

 possess a certain degree of elasticity and rigidity, since^ 

 in so far as they are less rigid, they do not contain 

 nitro-aerial particles in suflftcient abundance nor can 

 these be driven out or drawn out quickly enough. 



It is also clear from the aforesaid hypothesis why air 

 passes up in a continual stream to support combustion. 

 For I do not think that this should be ascribed merely to 

 the rarefaction of the air mixed with the flame : but 

 because the aerial particles mixed with the flame are 

 deprived of nitro-aerial particles, and therefore also of 

 elasticity, it comes about that they are no longer able 

 to resist the pressure of the ambient air. Hence such 

 particles of air as are nearest press into the place of 

 the ignited particles of the air and drive them up- 

 wards, since they have lost not only elasticity but also 

 their former weight in consequence of the disruption 

 from them of the extremely solid nitro-aerial particles. 

 And thus one particle displaces another and the flame 

 is renewed by a fresh access of air. The following 

 experiment points also to the same conclusion, viz. : — If 

 a small animal such as a mouse or a bird is enclosed in 

 the manner aforesaid at the top of a glass vessel it will 

 die much sooner, and the water underneath will rise 

 much less than if the same animal had been placed in 

 the lower part of the glass. This will be very manifest 

 if two birds or two mice are enclosed at the same time, 

 one in the upper and the other in the lower part of 

 the glass ; for in this case the animal put in the 

 lower part of the glass will for some time survive the 



