( 667 ) 



/ é 



10 t> iO 



spoil the drawing, the tube has l)eeii cut near S\ cue must iuiagine 

 between tlie two /S"s a piece of tubing, about 50 cm. long). Neither 

 the lower nor the upper side (►!' .1 lias been luxrrowed, so as to 

 facilitate the cleaning of the tul>e. 



After the mercury vessels have been [)roperl3' filled and the 

 apparatus connected, the air is rarefied by means of a powerfully 

 acting removable water-pump. In consequence the mercury rises in 

 A, B and C. 



Wheii the requisite pressure is attained, A is raised by means of 



