g54 BAROMETRICAL MEASUREMENT OF HEUiHTS. 



Table I. gives the corresponding numbers, < 



h = 8183.5 

 6280.8 



Difference, 1902.7 



Table II. gives for T' — T, — 5.2 



Difference, 1897.5 = N 



^.2{t-\- //) = 1.897 X 93.2, + 176.8 



Sum, 2074.3 



Table Til. gives for mean latitude of 21°, -|- 4.3 



Table IV. gives for decrease of gravitation in the vertical line, -|- 6.0 



Hence altitude of Guana.xuato above the ocean, 2084.6 



Measurement of the height of Mont Blanc, August 29, 1844. By MM. Bravais 



and Martins. 



mm. o c 



Barometer at one metre below the summit, h' = 424.05 T' = — 4.2 f = — 7.P 

 Barometer of the Observatory of Geneva, h =729.65 T = 18.6 t = 19.3 



„ ^, , . » ^ J. i h = 7826.0 



lable I. gives lor numbers correspondmg to < oc.a/« 



Difference, 4321.6 



Table II. gives for T' — T, — 29.3 



Difference, 4292.3 ^ N 



^. 2 (/ -f t') = 4292 X 23.4 = + 100.4 



Sum, 4392.7 



Table III. gives for the mean latitude of 46°, — 0.4 



Difference, 4392.3 



Table IV. for decrease of gravitation in the vertical line -(- 13.7 



Table V. for the elevation of the lower station, -|- 0.5 



Sum, 4406.5 



Elevation of the lower barometer above the ocean, 407.0 



Hence elevation of upper barometer above the ocean, 4813.5 



Finally, height of the summit of Mont Blanc above the ocean, 481 1.5 



D 14 



