J823.] for Barometrical Measurements, 363 



consequence authorized to conclude, that the formula of M. 

 Laplace keeps nearer the truth, and is less dependant on varia- 

 tion of temperature than the others." 



He then proceeds to point out the divergence of the other 

 formulas from the truth according to variations of the temper- 

 ature. 



The second part of this memoir is devoted to an examination 

 of the correction for the diminution of gravity corresponding to 

 the latitude. The accuracy of the expression for this purpose 

 given in the formula is shown by a comparison of M. Hum- 

 boldt's observations with geometrical determinations of the 

 heights of several mountains in Mexico and Peru. 



The third part treats of the correction for the vertical diminu- 

 tion of gravity. An extensive comparison is made of the results 

 of observations, employing in the first instance the exact formula 

 comprising the correction in question, and in the second, dis- 

 pensing with that correction by an augmentation of the constant 

 coefficient from 18336 m. to 18393 m. Fourteen measurements 

 are thus compared, and the results differ but little. At the end 

 of the memoir an example is worked out by both methods. The 

 difference is about nine feet in the height of Chimborazo. 



In the fourth part M. Ramond examines the results deducible 

 from the formulae which he had before compared together, in 

 relation to the ratio which they respectively give between the 

 weights of air and mercury ; comparing also this ratio with that 

 given by experiment. 



He commences by reducing each of the four formulae of 

 Laplace, Trembley, Kirwan, and Shuckborough, to a similar 

 form, thus separatmg in each the corrections for the temperature 

 both of air and mercury, and the constant coefficient, both whea 

 taken with the mean constant correction as examined in the 

 preceding part, and when uncorrected. 



Laplace. 



Ord. coefF.7 loooo 

 t.0°lat.455^^^^^ 

 Coeff. re--) 

 duced to V 18336 

 level of sea J 

 Factor for' 

 tempera- 

 ture 



Dilatation 7 i 

 of mercury 3 mTs 



;or for^ ^ 

 '"^-. \ 25b 



01 air J 



Trembley. Kirwan. Shuckborough, 



18322-976 18287-83 18425-188 



18266-193 1823M56 18368-088 



1 I 1 



225-625 



1 



5400 



222-2222 



1 

 6020 



2540625 



1 



5400 



From each of these the resulting ratios of the weights of air 

 and mercury are as follows : 



