1 12 Mayow 



tions caused by the effervescence will rise in the 

 form of bubbles to the top of the glass and constitute 

 the air there, which, gradually increasing, will de- 

 press the underlying water. Let the glass, when it 

 is completely filled with air of this kind, be raised a 

 little, that the iron globules, which are to be removed 

 from the liquid, may escape from it, care however 

 being taken that the mouth of the glass be not raised 

 above the liquid. And so we shall see that air which 

 occupied the whole glass, gradually condense, and the 

 underlying liquid rise into its place. And yet this 

 air will not all become liquid, for the glass will be 

 always about one-fourth filled with it ; and this air, 

 however long kept, even in the coldest weather, will 

 never be condensed intQ a liquid. If the iron globules 

 be placed under the mouth of the glass while it is still 

 inverted and put a second time into it, air will be 

 produced anew, a certain part of which will never 

 become liquid. So that the glass will be about half- 

 filled with exhalations that will never be condensed. 



If oil of vitriol mixed with water be substituted 

 for spirit of nitre, or if a very sluggish fermentation 

 be excited in the manner described, or also if the 

 iron globules be allowed to remain in the glass for a 

 day or two, then the air generated in this way will 

 scarcely suffer condensation at all. For the partial 

 contraction of the air in the aforesaid glass was due 

 to this, that the exhalations produced by violent 

 fermentation were agitated with a very rapid motion, 

 which, gradually abating, the air was reduced to 

 smaller bulk ; while, if the fermentation has been 

 mild and has gone on for a long time, the exhalations 

 generated later will take up and fill the place left by 

 those previously condensed, so that the air will 

 scarcely suffer any condensation at all. 



