400 BAROMETRICAL MEASUREMENT OF HEIGHTS. 



Example 2. 

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



In this case, assuming t = i', 



2 r = ^^ =.= — 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 

 W^e have u = 92.6 



-155^ = + 6-«' 



98.67 

 With h\ in Table II., take H' = 826.22 



H = 924.89 



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

 give b = 338.54 lines. 



II. For Computing Differences of Elevation from Barometrical Observations. 

 Suppose to be given B, B', T, T', ^, ^', ^ ; required h. 



Make first t = -"t^ and T — T'. 



4 



Then in Table II., with the argument -; r>/ . i tt/ 

 ' ° ( B' take H', 



and make 



u = (H - H) + ^1-^' r - (T - TO, 



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



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



in T'able IV., with u and 0, 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 



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



then in Table II., with the argument, < ,, ' , yy/ 

 and make 



„ = H - H' + - ^^ r. 



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

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

 and 



D 60 



