I. 



TABLES 



I 

 FOR 



DETERMINING DIFFERENCES OF LEVEL BY MEANS OF 

 BAROMETRICAL OBSERVATIONS, 



COMPUTED FROM THE COMPLETE FORMULA OF LAPLACE, 

 BY M. T. DELCROS. 



Construction of the Tables. 



If we take z = difference of level of the two barometers, 

 a = earth's mean radius = 6366200 metres, 

 L = mean latitude between the two stations, 

 and further : 



f h = observed height of the barometer, 

 Lower. < T = temperature of the barometer, 



C t = temperature of the air, 

 ' . r , , . , ' 



f h f = observed height of the barometer, 



Upper. < T' = temperature of the barometer, 



C t' = temperature of the air, 

 and if we make finally H = h -f- h 1 . ( eioe^)* 

 we shall have, according to Laplace, the following general and complete equation 



t = 18336 metres X I ( * + 0.0028371 cos. 2. L) 



((1 + i). Log. (A) + i 0.868589) 

 after the proper transformations this equation becomes : 



C __ 



\ -- 1000- 



| ( 1 + 0.0028371 cos. 2. L) 



. . . 



. = Log. (,) 18336 n^es X <j , (log . (1)+0 . 868589) .^ 



[V Log. (IT t 



D 11 



