202 Experiments on the Prodtiction of Air 



or hoop of soft wood was nailed down upon the board 

 in that part. 



By this arrangement the jars were spared, and the end 

 of the neck of the globe being easy to be come at, by 

 introducing a wire, or, what I commonly made use of ^ 

 in preference, a small glass tube, into the globe, the air 

 hanging attached to the silk can at all times be separated 

 from it ; which is often necessary, in order to determine 

 with greater precision the quantity of air furnished in 

 any given time. 



The air produced naturally rises to that part of the 

 globe which is uppermost, where it collects in a body, 

 driving out an equal volume of water ; which, to prevent 

 its running about, may be collected by placing a proper 

 vessel under the mouth, or end of the neck of the globe, 

 to receive it. 



The method of removing the air from the globe is too 

 well known to require a description. I would, however, 

 observe that, in doing it, care should be taken that the 

 water in which the globe is immersed be quite clean, 

 and of the same kind with that in the globe, otherwise 

 that which enters the globe, to replace the air removed, 

 might derange the experiment. 



Having provided myself with a number of globes of 

 different sizes, all fitted with boards or stands to support 



