BAROMETER TO SEA LEVEL. 5 
From (iv.) and (v.), together with (vi.), we may deduce (ii.), thus : 
In (iv.), let 6 = 8, we obtain 
i Ce . (CaO. 
gh, 1 Re LW BW, 1008 
4 1 Z Z 1 
Pa ie 42 1 ee) Me 
MA gis & Z Z 1 1 
i EN pt eens + F See ee ey oe eee 
- (.%.t2 ) B= a5 + 1.2 10 bp, my stone 
But from ({vi.) B. Be, =a am, nearly. 
2Z ; Ba 1 1 
N =_ ——- * —-* ———s— i 
er, neglecting the second term on the right, 
4 QZ ae 
= += => nearly. 
gue +o 1 y 
Here ¢ is the mean between the temperatures at the upper and 
lower stations; whilst in (ii) these two temperatures are respec- 
tively employed, in taking out the two numbers. The difference 
thus imtroduced is very triflimg ; as may easily be seen, if the value 
given below for A, , be substituted in the expression for NV, 
Formula (ii.), like (v.), is objectionable, in that it assumes a know- 
ledge of the reduced reading, which it is the object to ascertain. 
