281 

 Table XIX. 



This table has been calculated by using the following coefficients of dilatation : — 

 Brass, linear dilatation, from Laplace and Lavoisier for 100° C. = 0.0018782. 

 Mercury, dilatation in volume, from Dulong and Petit for 100° C. = 0.0180180. 

 Dilatation of the mercurial column for 100° C. . . . = 0.0161398. 

 Dilatation of the mercurial column for 1° C. . . . = 0.0001614. 

 Observed height reduced to freezing point, 



H=A — /t (0.0001614). T=h — h(^^). 

 The second term of this last formula is given by the table, when the temperature 

 T and the height h of Lie barometer are known ; this correction must be subtracted 

 from the observed height h, when the temperature is above freezing point ; it is to be 

 added when the temperature is below zero, or freezing point. 



This table allows the barometrical heights taken at the highest summits, and n the 

 deepest mines, to be corrected. 



Examples of Calculation. 



mm. 



Barometer, observed height, . . . • . 567.49 



Temperature of the barometer, -j-lS".?. 



o mm. 



r for 10.0=0.912 



Second page, < for 2.0 = 0.182 



C for 0.7 = 0.064 



Total, = 1.158 

 SvJbtractive correction, — 1.16 



Barometer at zero, 566.83 



mm. 



Barometer, observed heiffht, . . , , , 454.17 

 Temperature of the barometer, — 7°. 8. 



o mm. 



C for 7.0 = 0.514 



rirst page, < „ ^ ^ 



^ ^ ' /for 0.8 = 0.059 



Total, = 0.573 

 Additive coriection, -j-0.57 



Barometer at zero, 454.74 



75 



