1823.] Measurement of Heights ht/ the Barometer, §S 



Article IIL 



An Abridged Translation of M. Ramond's Instructions for the 

 Application of the Barometer to the Measurement of Heights^ 

 with a Selection from his Tables for facilitating those Opera^ 

 tions, reduced (tvhere necessary) to English Measures, By 

 Baden Bowell, MA. of Oriel College, Oxford. 



(To the Editor of the Annals of Philosophy.) 

 SIR, 

 The dissertations and tables of M. Ramond are of such 

 acknowledged excellence for the purposes of the barometrical 

 observer, that I trust the following abstract ofthem brought into 

 a form more convenient to the Enghsh student will not be unac- 

 ceptable. On a careful perusal of his pubhcation, it appeared to 

 me that the valuable informationcontainedinitwas very suscep- 

 tible of being reduced into a smaller compass ; and that among 

 the various tables he has given, those of more essential use 

 might be selected, and, as far as requisite, reduced to English 

 measures. In this way I conceive the most valuable materials 

 of the author may be very usefully collected ; and within the 

 compass of three, or at most four papers of such length as is 

 proportionate to the size of a number of the Annals^ I trust I 

 shall be able to present the scientific inquirer with a compen- 

 dium of much information highly requisite to be attended to in 

 the measurement of heights by the barometer, and with a set of 

 tables which seem to unite facility of operation with correctness 

 of result, in a greater degree than any extant. B. P. 



General Principles of Barometrical Measurement, 



It is well known that in the barometer the mercury sinks as 

 we are elevated above the level of the sea ; this indeed must be 

 the case, for the barometer may be considered as a balance in 

 which the column of mercury keeps in equilibrio with the corres- 

 ponding column of air. At the level of the sea, it balances the 

 whole weight of the atmosphere : at a greater elevation, only a 

 part of it. The quantity by which it has sunk expresses the 

 weight of the stratum of air intercepted between the levels of the 

 two stations. Considered in relation to the measure of height, 

 it expresses the difference of level in a ratio depending on that 

 of the densities of mercury and air. What then is the thickness 

 of the stratum of air whose weight is equal to that of an inch of 

 mercury ? To such a question may the problem of the mensura- 

 tion of heights by the barometer be ultimately reduced. This 

 question, however, apparently so simple, has nevertheless occa- 

 sioned much difficulty to philosophers. 



