1823.] the Barometer to the Measurement of Heights. 265 



In continuation of this brief summary of what M. Ramond 

 considers the most necessary rules for conducting the observa- 

 tions, 1 will here, for the sake of those who may be less versed 

 in the use of tables and formula, reduce into rules the method to 

 be observed in performing the calculations. 



1. From the common tables of logarithms take the log. of the 

 height of the lower barometer. 



2. Apply the correction according to its sign from Table I. 



3. From this result subtract the logarithm of the upper baro- 

 meter. 



4. Take the logarithm of this difference supposing it a natural 

 number. 



5. Add the logarithm of the constant coefficient. 



Q^ . correction. Table II. 



7. — Table III. 



8. . correction for temperature de- 

 scribed in the second section. 



The natural number corresponding to the resulting logarithm 

 is the true elevation in feet. 



I subjoin an example. 



If the shorter formula is used, the seventh step will be dis- 

 pensed with. 



Example, 



Centigrade. 



Lower station. 

 Upper station. 



Bar. in inch. 



... 29-882 

 ... 24-409 



Bar. in metres. Ther. of bar. Air therm. 



Lat. 



•759 

 •620 



.. 15 

 ,. 10 



DifF. 5 



.... 14 

 6 



Sura 20 

 Double 40 



Log. of lower barom, in inches. ... 1 •475409T 

 + correction. Table 1 9-9995990 



•475008T 



;. upper barom. in inches. 



0-0874587 



Log. of metres 1 -880241 8 1 

 9-9995990 



1-8798408 



>* 



•3875500 -Log. of metres 1-7923823 



= 00874585 



Log. of difference of logs 2-9417995 



Leg. of constant coefficient 4-7792962 



Correction for latitude. Table II. 9-9993835 

 Correction, Table III. Diff. of) 

 logs. -08. Double sum of> 0-0012323 



the thermometers 40 ) 



^ ^ 1000+40 ,^,^^ 



Corr. for temp. — — — = 1 '040 / 



1000 



its log. 



0-0170333 



3-8916448 log. of 7791-9 ft.=height required. 



'* The same result would obviously be obtained, by whatever seal? the barometers 

 were divided. 



