IV. 



TABLES 



FOR REDUCING BAROMETRICAL OBSERVATIONS TO THE LEVEL OF THE SEA, OR TO AN^i 

 OTHER LEVEL, AND FOR COMPUTING DIFFERENCES OF ELEVATION MEASURED BY THI 

 BAROMETER, BY M. C. DIPPE. 



THE following tables, published by M. C. DIPPE, in tbe Astronomische Nachrichten 

 No. 1056, November, 1856, are a modification and extension of Gauss's tables 

 published in Schumacher's Jahrbuch, for 1836 and the following years, which are 

 based on the formula of Laplace. In this new form they answer a double purpose 

 They give the means of solving a problem which often occurs in Meteorology, viz. 

 The difference of elevation between two stations, and the temperature of the air a 

 both, being known, to reduce the height of the barometer at one of the stations to the 

 height it would have at the other. They are likewise adapted to the computation 01 

 heights from barometrical observations. 



The formula of Laplace, which has been used, the Metres being reduced to Toises 

 and the Centigrade degrees to degrees of Reaumur, reads as follows : 



h = 9407.73 



Where t and V = the temperatures of the air, in degrees of Reaumur, at the lowei 



and upper station, 

 b and If = the height of the barometer, in any scale, reduced to the freezing 



point, at the lower and upper station, 



h = the difference of level, in toises, between the two stations, 

 r = the distance, in toises, of the lower station to the centre of the 



Earth, 



<j> = the latitude of the place of observation, 

 a = the increase of gravity from the equator to the poles. 



Making, besides, m = the modulus of the common logarithms, the formula be- 

 comes, with sufficient accuracy, 



' ij^.^-L-^ ' 



400 ' T 



Assuming r, or the radius of the Earth, at 45 latitude = 3266631 toises, anc 

 a = 0.002595, instead of 0.002845 adopted in Gauss's tables, and making 



u = log b log b^ 



/ 1 1 2m 



'g (9407.73 



c = m a cos 2 <, 



' = -, 



then the reduction of the height of the barometer to another level is given by the 

 formula, 



D 54 



