Baron Cuvier's Historical Eloge of Baron Ramond. 17 



The mercury is supported in the barometer by the weight 

 of the atmosphere: in proportion as we ascend, the column 

 of air which presses upon it diminishes, it falls in the tube, 

 and if the air were everywhere of the same density and the 

 same temperature, nothing would be easier than to know by 

 its fall how high we had ascended : But it is not so. The 

 air being elastic, the superior compresses the inferior strata, and, 

 in proportion as we ascend, the density and weight of the air 

 decrease in a geometrical progression. The mercury then falls 

 less for an equal height, in proportion as this height is taken at 

 a higher elevation, — a second variation, which, if it were the 

 only one, would occasion only very simple operations. It would 

 have been sufficient to multiply the difference of the logarithms 

 of the observed heights of the mercury by a number which ex- 

 pressed in metres the elevation, which, at a given position, 

 at the level of the sea for example, corresponded to a determi- 

 nate fall of the mercury. But we should still obtain from this 

 rude results : the differences of heat both of the air and of the 

 mercury ; the differences in the humidity of the atmosphere ; 

 the decrease of the force of gravity arising from the distance 

 to which we are removed from the centre of the earth, and 

 even from the increase of the convexity of the globe towards 

 the equator, are so many circumstances which it is necessary 

 to take into account if we wish to arrive at any precision. 

 The late M. de Laplace had introduced all the operations which 

 these circumstances require into a general formula, which was 

 a rigorous expression of them, but the application of which 

 presupposed the positive determination of the coefficients 

 belonging to each, and particularly the principal coefficient; 

 but in his first trials he had fixed this coefficient too low, 

 so that all heights calculated from the formula were be- 

 neath the real height, as given by trigonometrical measure- 

 ments or by levelling. M. Ramond,* availing himself of some 

 heights measured accurately by geometers, and having made 



• Memoires sur la formule barometrique de le Mecanique Celeste, et les 

 distribution de Tatmosphere qui en modifient les proprietes, augmentes 

 d'une instruction elementaire et pratique destinee a servir de guide dans 

 rapplication du barometre a la mesure des hauteurs* Clermont-Ferrand, 

 1811, in 4to. 



UEW SERIES. VOL. II. NO. I. JAN. 1830. B 



