BAROMETRICAL MEASUREMENT OF HEIGHTS. 



Example 2. 



Suppose I' = 330.46 Paris lines ; t' = — 12°.3 Reaumur ; h' = 92.7 toises ; 

 (^ = 62°. 



In this case, assuming t = i', 



2t= ^^ = — 12°.3 ; r = — 6.15 ; 

 and according to Table I. t' = — 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 



100 



-f 6.07 



98.67 

 With b', in Table II., take H' = 826.22 



H = 924.89 

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

 give b ■= 338.54 lines. 



II. For Computing Differences of Elevation from Barometrical Observations. 

 Suppose to be given B, B', T, T', t, t\ cf) ; required h. 



Make first r = ^-i^ and T — T'. 

 4 



Then in Table II., with the argument ■] d^ j k tt/ 

 and make 



ri = (H_H') + ^/'r-(T-TO, 



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 m and <j), 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 = m4-C + C' + C". 



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



b take H 



and make 



and 



then in Table II., with the argument, •! i/ * u ti/ 



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

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



h = u -\- C -{- C. 

 D 62 



