164 A, Guyot on the Appalachian Mountain System. rag 
of the barometric tube and which is so placed as to make its in- 
dications accord with those of the normal barometer. A line 
traced on the fixed scale marks the natural height of the column 
of mercury and makes apparent the value of the applied cor- 
rection. 
not only stronger, but it greatly facilitates the cleansing of the 
mercury, which it is well to attend to frequently. Finally it dis 
now in use throughout America, having been substituted for 
those of Bunten in the army meteorological stations, and having 
servations I would mention that they have been constantly: 
companied by corresponding observations made by my young 
