So Mayow 



duced in iron by nitro-aerial particles communicated 

 to it from fire, as I previously endeavoured to show. 

 I am also of opinion that the elastic force of the air 

 consists in this that the particles of the air becoming 

 rigid, and compressed and bent by the weight of the 

 incumbent atmosphere, strive to spread themselves 

 out. 



Certainly the rigidity of the aerial particles seems 

 to be the cause of their not entering the minute 

 pores of bodies so readily as the grosser particles 

 of watery liquids, as could be established by very many 

 experiments. For although aerial particles are very 

 minute, yet on account of their rigidity they cannot 

 adapt their forms, like the flexible particles of watery 

 liquids, to the tortuous passages of bodies. Hence also 

 it seems to come about that water ascends in very 

 minute glass tubes and also into the pores of a sponge 

 and other things of that kind. For although rigid 

 particles of air cannot enter extremely fine little pores 

 of that sort, yet water is forced up into them as into an 

 empty space by the pressure of the remaining air. 



To this I add further that the rigidity of aerial 

 particles appears to contribute not a little to the 

 kindling of fire, inasmuch as the nitro-aerial particles 

 on being violently torn from the particles of the air in 

 which they were firmly fixed are thrown into very rapid 

 motion, for otherwise I do not see how the nitro- 

 aerial particles could begin so rapid a movement. But 

 of this more will be said afterwards. 



But now it is probable that aerial particles when 

 mixed with flame lose their elasticity in the following 

 manner. Thus we must suppose that the sulphureous 

 particles of fire, when thrown into violent agitation, 

 approach all the particles of air which are nearest 

 them, and impinge on the nitro-aerial particles which 



