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, 



ii-=;i_/i (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 the barometer are known ; this correction must be subtracted 

 from the obseiTed height Ji, 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 in the 

 deepest mines, to be corrected. 



Examples of Calculation. 



mm. 



Barometer, observed height, 567.49 



Temperature of the barometer, -{-12°. 1. 



o mm. 



r for 10.0=0.912 



Second page, } for 2.0 = 0.182 



C for 0.7 = 0.064 



Total, = 1.158 

 Suhtr active correction, — 1.16 



Barometer at zero, 566.33 



mm. 



Barometer, observed height, 454.17 



Temperature of the barometer, — 7°. 8. 



o mm. 



for 7.0 = 0.514 

 .059 



o '■" 



C for 7.0 = 0.^ 

 First page, | ^^^ ^.8 := 0.( 



Total, = 0.573 

 Additive correction, -|-0.57 



Barometer at zero, 454.74 



75 



