348 On Ilypsomelrical Measurements. [No. 4. 



T'—T' 



(4) 



log B - log B' 



and hence when B = B', and T = 100° cent, using Moritz's values, 

 we have 



dT B.dT 



n — = _ =± 64.307626 . . (5) 



d. log B M.dB 



and when T' = 80° C, we have, by equation (4) — 



20 

 n 80 = — = 60.412836 



lo g B ioo — lo S B ' 8 o 

 and as the value of n is found to vary pretty regularly with the 



temperature between these two points, we may write — - 



n, nn — n, 



loo '"8 



n T = 64.30763 — (100 — T) 



20 



= 64.30763 — 0.1947445 (100 — T) (6) 



Substituting this value in equation (4) we find — 



100° — T 

 Log B — log B T = — 



64.3076 — 0.19474 (100 — - T) 

 5.13493 (100 — T) 



(7) 



330.215 — (100 — T) 



We obtain a result almost identical with this by applying the 



method of least squares to the logarithms of Moritz's tensions 



at 80°, 85°, 90° and 95°, viz.— 



5.108555 (100 — T) 



LogB 100 -logB T = .. (S) 



328.62566 — (100 — T) 



either of the equations (7) and (8) will give the logarithms of the 

 pressures in millimetres of mercury for temperatures between 80° 

 and 100° C. generally correct to the 5th or 6th decimal place, by 

 using the following values. 



mm. 



For log B 100 = log 760 2.8808136 



For log 5.108555 0.7082981 



If now we combine equations (2) and (8) and introduce the value 

 of L for a standard atmosphere at 0° Cent, the approximate height is 



