ON COMPRESSED AIR. 209 



and appeared to be viewed by them all, as 

 equally new and extraordinary.* 



Mr. Roberts made some experiments on his 

 air-valve at the time, and various theories were 

 then suggested to account for the adherence of 

 the valve to the pipe. It was not, however, until 

 the month of September in the present year, 

 that I agreed to join him in making further 

 experiments, a part of which, I now proceed 

 to give. 



A vertical section of part of the apparatus used 

 is given in figure the first, where A is a pipe 3 

 inches diameter, with the aperture contracted 

 to 2| diameter ; B B surrounded by a flange C C, 

 lOi diameter, to form a seat for a valve. On 

 this seat was placed a circular disk or valve D D, 

 6 inches diameter, with a pin in its center, by 

 means of which it was left at liberty to rise or fall 

 freely, and kept at the same time perpendicular to 

 the aperture. 



The valve was attached to one end of a scale 



* Monr. Clement, of Paris, was, I understand, in Manchester 

 at this period, and saw the air-valve adhere to the pipe, yet 

 he afterwards, it appears, represented the discovery to have 

 been made in France long subsequent to the time he saw it at 

 Mr. Roberts' works. 



2 D 



