I. 



T ARLES 



DETERMINING DIFFERENCES OF LEVEL BY MEANS OF 

 BAROMETRICAL OBSERVATIONS, 



COMPUTED FROM THE COMPLETE FORMULA OF LAPLACE, 



By M. T. Delckos. 



At Station. 



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 : — 



r h = observed height of the barometer, 

 Lower, s T = temperature of the barometer, 

 (, t = temperature of the air, 

 ^ h' =1 observed height of the barometer. 

 Upper. < T' = temperature of the barometer, 

 (, t' = temperature of the air, 

 and if we make finally H = h -{- h'. ( eidl' )^ 

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



V r 1000 / 

 z = 18336 metres x j ( 1 + 0.0028371 cos. 2. L) 



, ((1 + ^). Log. (A) 4_ A 0.868589) 

 after the proper transformations this equation becomes : — 



r(i+^-') 1 



z = Log. (4) 18336 metres X 



I ( 1 4-0.0028371 cos. 2. L) 



D 



(' »g- (w) + 0-86858 9) . i 

 Log. (4) 



V 



