- T) S J 



350 On Hypsometrical Measurements. [No. 4. 



mm. 



Log B T = log 760—0.01555026 (100° — T) 



— 0.0000464227 (100° — T) 2 — 0.00000018515 (100 c 



By means of equation (10), Table V. has been constructed, giving the 

 logarithms of the pressures in inches of mercury for every fifth 

 part of a degree from 176° to 215° F. ; and from the same equation 

 we derive for Fahrenheit's scale — 



B. dT 



n = — = 115.71976, 



and from the table, by least squares, — 



m. 212» — T 



Log 30 — log B T = 



115.71976 — 0.1957 (212 — T) 

 5.108273 (212 — T) 



(11) 



379.319 + T 



where log 5.108273 = 0.7082741. 



And, as before, the elevation in feet above the point where water 

 boils at 212° Eaht. will be found by multiplying the right hand side 

 of this equation by L = 60369 feet, viz. : 



308382 (212 — T) 



379.319 + T \ (12) 



or log h = 5.488089 -f- log (212 — T) — log (379.319 + T). 



5. If the boiling-point be observed at two stations, whose difference 

 of level is required,— writing D = 212° — T, and D' for 212°— T', 

 we have, — 



308382 (T — T') 



h'—h = 



167.319 + (T -f T') + 0.00169 DD' 



1 VD 



or, since 0.00169 is very nearly , we may use 



600 ' 600'' K 13 ) 



.-. Log Qi — h) = 5.488089 + log (T — T') 



— log (167.319 + T -f T' + ) 



600 J 



