1858.] On Hypsometrical Measurements. 355 



By Table VI. height corresponding to 185M9 14645 feet. 



By Barometrical Tables the diff. of heights ") r,^ 



corresponding to 30 ln * and 29 in \063 j 



Difference, or approximate height, 13811 



| (t -f- 1') = 55°, Multiplier from Table 1 1.0497 



Corrected height, as before, above Geneva, 14497 ft. 



'Example III. (Boileau's Tables, Int. p. xix.) At the Parang 

 Pass in lat. 32°J N. the observed temperature of the boiling-point 

 was 179°.3, the temperature of the air being 27° F. to find the 

 altitude of the pass above the level of the sea. 

 Here, by the formula, \ (ii -f t') = 27° + 0.9 (212 — 179.3) = 56°. 



Approximate height by Table VI 18052 feet 



i (t + tO = 56° .. Multiplier by Table I. 1.0517 



Corrected height above sea-level, 18985 feet 



differing from Boileau's result principally from the higher value 

 assigned to t, and partly from the standard pressure in Boileau's 

 table being 29 ln, .921 instead of 30 in# , which gives a difference of 

 about 60 feet in the elevation. 



12. A small correction ought to be applied on account of the 

 variation of the pressure at the level of the sea in different 

 latitudes from a standard of 30 inches. Tables V ahd VI are 

 calculated on the hypothesis that the pressure of the atmosphere 

 at the level of the sea is 30 inches. Observations prove that the 

 mean pressure varies in different latitudes, and according to the 

 experimental and theoretical observations of Munke and others, the 

 following short table has been constructed shewing, in column (2), 

 the height of the barometer in different latitudes equal to a height 

 of 30 inches in lat. 45°, in columns (3) and (5) the mean heights of 

 the barometer as derived, with some modifications, from Munke and 

 Dr. Golding Bird* respectively, and in columns (4) and (6) the 



Dr. Golding Bird's Natural Philosophy, p. 208. 



