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=h h (0.0001614). . T=h h ( 6 -^ 6 ). 



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 7i, 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, -f-12.7. 



o mm. 



f for 10.0=0.912 



Second page, < for 2.0 = 0.182 



C for 0.7 = 0.064 



Total, = 1.158 

 Subtractive correction, 



Barometer at zero, 



mm. 



Barometer, observed height, 454.17 



Temperature of the barometer, 7. 8. 



o mm. 



_. 4 C for 7.0 = 0.514 



First page, < 



Additive correction, 



Barometer at zero, 454.74 



75 



. +0.57 



