BAROMETRICAL MEASUREMENT OF HEIGHTS. 



TABLE X. 



CORRECTION FOR THE HOITR OF THE DAY. 

 ARGUMENT, THE HOUR, AND THE APPROXIMATE HEIGHT IN TOISES. 



Table XL is found in the Resume des Observations Thermometrique et Barome- 

 Hquesfaites a Geneve et au Grand St. Bernard pendant les dix annees 1841 d 1850, 



very elaborate paper by Professor E. Plantamour, Director of the Observatory at 

 Jeneva, published in Vol. XIII. of the Memoires de la Societe de Physique de Geneve. 

 Hie author, after having determined the difference of elevation between Geneva 

 407.0 metres above the level of the sea) and the Great St. Bernard, by means of 

 he corresponding observations, made during these 10 years, and using his own tables 

 jiv^n above, reversed the problem. Assuming the difference of level thus found, 

 p iz. 2066 metres, to be the true height of the layer of air between the two stations, 

 md its weight being given by the barometrical observations, he deduced from these 

 lata its mean density, and from the density its mean temperature at every even 

 lour in every month of the year. Comparing these mean temperatures with those 

 jiven at the same hours by the half-sum of the temperatures taken at the upper and 

 he lower station, he found the differences contained in Table XL, which are the cor- 

 ections to be applied to the half-sums of the temperatures to obtain, in this particular 

 ase, the true mean temperatures. The second part of the table has been computed 

 >y multiplying each temperature in the first by 7.5 metres, in order to show the value 

 f that correction in barometrical measurements. 



D 81 



