17? Mayow 



aqueous particles has been placed beyond all doubt 

 by Boyle's experiments ; for if spring or rain-water 

 be put in a glass from which the air is exhausted by 

 suction, innumerable little bubbles, formed of the 

 substance of air, will burst from it. In fact, as soon 

 as the pressure of the atmosphere is almost removed, 

 the aerial particles dispersed through the mass of the 

 water immediately open and stretch out in virtue of 

 their elastic force ; so that the little portions of air 

 which previously lay hidden and quite inconspicuous 

 in the pores of the water, now swell into little bubbles 

 which are forced upwards on account of their lightness. 

 Moreover, that air resides in the small pores of water 

 will be further proved by the following experiment. 

 For let a small glass be placed in such a way under 

 water contained in a suitable vessel, that all the air 

 may escape from it and water enter in its place. 

 Then let that glass, filled with water, be inverted and 

 placed at the bottom of the said vessel, and let it 

 remain so, much as in Plate V., Fig. 3. After these 

 preparations, let the vessel into which the inverted 

 glass is put be placed on the fire so that the water 

 contained in it may be heated, and then let the vessel 

 be removed from the fire so that the water may again 

 cool. When this is done, we shall find that the top 

 of the inverted glass is occupied by a kind of air 

 partly composed of the vapours raised from the 

 boiled water and not yet completely condensed, but 

 partly of aerial matter. For since the air mixed with 

 the water contained in the glass is rarefied by the 

 heat of the fire, and consequently occupies more space 

 than formerly, it is raised in the form of little bubbles 

 to the top of the glass by the pressure of the 

 surrounding water. And that this aerial matter is in 

 part air, I infer also from this, that a certain portion 



