Dr. Harems Improved Barometer Gage Eudiometer. 281 



^ a 



Description of the Gage. 



It is well known, that if a vertical glass tube communicate, through 

 its upper orifice, with a receiver, while its lower orifice is situated 

 beneath the surface of an adequate quantity of mercury, in any con- 

 venient receptacle ; on exhausting the receiver, the metal will rise 

 in the bore of the tube in proportion to the quantity of air removed. 

 Hence, if zero of the ascending column of degrees, counting upwards 

 from one to ten, be placed on a level with the surface of the mercury 

 in the receptacle at the foot of the gage tube G, the quantity of gas 

 liquefied or withdrawn will be as the number of degrees opposite 

 the surface of the column of the mercury in the gage tube. 



Again, supposing it were possible to exhaust the vessel perfectly, 

 the column of mercury in the gage, would attain the height of a well 

 filled Torricellian tube. By having such a tube by the side of the 



Vol. XXXIL— No. 2. 36 



