158 Analyfis of the Air. 



head into a large veffel of water, to a the 

 top of the bolthead ; as the water rufhed in 

 at the bottom of the bolthead, the Air was 

 driven out thro* the fyphon : When the 

 bolthead was full of water to z, then I clofed 

 the outward orifice of the fyphon with the 

 end of my finger, and at the fame time drew 

 the other leg of it out of the bolthead, by 

 which means the water continued up to z> 

 and could not fubfide. Then I placed under 

 the bolthead, while it was in the water, the 

 veffel x x, which done, I lifted the veffel x x 

 with the bolthead in it out of the water, 

 and tyed a waxed thread at z to mark the 

 height of the water : And then approached 

 the retort gradually to the fire, taking care 

 to fcreen the whole bolthead from the heat 

 of the fire. 



The defcent of the water in the bolthead 

 fhewed the fums of the expanfion of the 

 Air, and of the matter which was diftil- 

 ling : The expanfion of the Air alone, when 

 the lower part of the retort was beginning 

 to be red hot, was at a medium, nearly 

 equal to the capacity of the retorts, fo that 

 it then took up a double fpace 5 and in a 

 white and almoft melting heat, the Air took 



up 



