BAROMETRICAL MEASUREMENT OF HEIGHTS. 



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 III. gives for mean latitude of 21°, -f 4.3 



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



Hence altitude of Guanaxuato above the ocean, 2084.6 



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



and Martins. 



mm. o o 



Barometer at one metre below the summit, h' = 424.05 T' = — 4.2 t' = — 7.6 

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



Table I. gives for numbers corresponding to \ 



h = 7826.0 

 3504.4 



Difference, 4321.6 



Table II. gives for T' — T, — 29.3 



Difference, 4292.3 = N 



^, 2 (< + 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, -f- 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, 4814.5 



D 16 



