BAROMETRICAL MEASUREMENT OF HEIGHTS. 



Example 2. 



Suppose I 1 = 330.46 Paris lines ; t' = 12.3 Reaumur ; h' = 92.7 toises 



= 62. 



In this case, assuming t = t' , 



2r=^= 12.3; r= 6.15; 



and according to Table I. r 1 = 6.55. 



With h and r, in Table III., take C = 0.2 

 With h and <, in Table IV., take C' = + 0.1 



Add h = _92.7 

 We have u = 92^6 ~ = 



u T< = 6.55 



98.67 _^ , 



With ', in Table II., take H' = 826.22 10 T ' 



U= 924.89 



With H, in Table II., we find b = 338.53 Paris lines. Gauss's tables (IV.) woul< 

 give b = 338.54 lines. 



II. For Computing Differences of Elevation from Barometrical Observations. 

 Suppose to be given B, B', T, T', t, t', <f> ; required h. 



Make first r = -tl and T T'. 



Then in Table II., with the argument j S/f \ 6 Vf> 



^ JJ LcttVL/ i J. ^ 



and make 



TT TT' 



100 



in which each full degree of T T' corresponds to a toise. 



Further, in Table III., with u and T, take C reversing the sign ; 



in Table IV., with u and <, take C' reversing the sign ; 



in Table V., with T T' and r, take C ' with the signs of T T'. 

 Then the difference of elevation required is 



A^M-j-C + C'-j- C". 

 If the heights of the barometer, reduced to the freezing point, or b and ', are given 



then in Table II., with the argument, | */ l ^ e ^j/ 

 and make 



100 

 Further, in Table III., take C reversing the sign ; 



in Table IV., take C' reversing the sign ; 

 and 



h = u + C + C'. 

 D 62 



