1825.] Barometrical Measurement of Heights, I7£i^ 



Table V contains the logarithms (exclusive of the index 4) 

 of the coefficients for dry air at different degrees and quarters 

 of a degree of the sum of the detached thermometers, including 

 an exact correction for the diminished specific gravity of the 

 mercury in the vertical line. 



Jlule. — 1. Affix to the observed heights of the barometers at 

 the two stations the corresponding tabular logarithms (rejecting 

 indices), which consider as natural numbers, and make the first 

 four figures to the left hand whole numbers, and the remainder 

 decimals. 2. Find the difference of these two numbers, gene- 

 rally termed the logarithmic difference. 3. Take out the loga- 

 rithm of that difference (still avoiding indices), and prefix to it 

 with an intervening decimal point, the number expressive of the 

 quantity of whole numbers contained in the logarithmic differ- 

 ence. 4. Add to this logarithm and index of whole numbers 

 the logarithm of the coefficient for the corrected sum of the 

 thermometers precisely as given in the table. 4. Find the natu- 

 ral number of the product, exclusive of the index, which will be 

 the altitude in feet, consisting of the quantity of whole numbers 

 denoted by the index in the product. 



rrra arii :, Example, 



PacificOcean 29-8781in. Log. 4763-53 

 Chimborazo 14-8296 ,, 1711-30 



Log. of 3042-23 (prefix. 4) = 4-483 192 

 Log. coefficient of tl^e cor, sum of therms. . . 109-5 0*799899 \ 



217/ 



Log. 5-283308 



Natural number of 283308 (the whole numbers 



being five) 19200-0 



Correction for the diminished specific gravity of " jK 



the air, sufficiently explained in the Table (IV) + 1 7*7^ * 



Correction for latitude 2°, Table III. + 54-4 



Altitude of Chimborazo , 19272- 1 feet. 



The calculation is effected with the pressures reduced to 

 32° F. The observations were, -,x _, j, 



Pacific Ocean 30-0005 in. (77-5)^ Log.4771-29 ' ' ■ 

 Chimborazo. . 14-8536 (50-0) 1718-32 



Diff. of attached therms. 27-5 3052-97 Log. =4-484723 



Log. of coefficient 0-800116 



5-284839 

 * Theiadications of the interior thermometew represented by the ( ). 



