396 Tables for determining Heights [No. 5. 



Thermometers. 

 Barometers, attached, detached. 



Example II. Lake, 29.950 50 49 



Mountain, 27.474 44 45 



Diff. 6 Sum 94 



Barometer colder station, 27.474 



Correction for 6° Tab. 1 017 



27.491 Factor Tab. II. 37.93 

 Lake, 29.950 „ 0.72 



Difference of the Factors, 37.21 



Sum of Thermometers 94°. Factor Tab. III. .. 62.36 



22326 

 11163 

 7442 

 22326 



Product, difference of altitude in feet, 2320.4156 



Here the Barometer at the lower station is less than 30 inches, 

 therefore the difference of the Barometric Factors is used. The Lati- 

 tude being 55° it appears from Table IV., that 2 feet may be subtracted 

 from the above result. 



Note on the construction of the Tables. 



Let T and T' be the temperatures of the mercury ; t and t' those of 

 the air, h and h' the heights (after reduction by Tab. I.) of the Barome- 

 ters, at the lower and upper stations, and A. the latitude of the place. 

 Also let H express inches of the Barometrical column generally ; then, 



T<^T' 

 Table I. H , being the correction of the Barometer for the 



9600 5 



expansion or contraction of mercury, depending on temperature. Which 

 correction, being applied to the colder Barometer, is additive. 



Table II. 1000 (209 30—209 H), and consequently the sum or 

 difference of the tabular quantities taken for h and h' is equivalent to 

 1000 (209 h— 209 V) ; five figure logarithms being used. 



