RECORD AND DISCUSSION OF ATMOSPHERIC PRESSURE. 87 



The constant c is, therefore, + 0.159 inches, at a mean temperature 75.7S and 

 a mean barometric pressure 29.831. To deduce the coefficients m and n, the cor 

 rection c has first been applied to the aneroid readings. The following differences 

 were then formed : B (A + c), (A + c) 29.831, and T 75.S. We then have 

 the 05 conditional equations: 



1. 0.079= +0.328 m 10.8 &amp;gt;i 



2. 0.034 = +0.258 m 3.8 n 



3. 0.072= +0.168 m 13.8 H 



4. 0.039 = 0.012 m 5.8 n 

 etc. etc. 



Their solution furnishes m and n. Making first the coefficient of n as great as 

 possible, by addition and change of sign of the equation when necessary, we find 



203. 4 n + 0.84Gm = +1.374 

 or, n=+O.OOG75 0.004m, 



and, in like manner, m results from the equation 



12.56 m + 40 = +1.190 



m = +0.072, and n = +0.0065 



Hence the formula for reduction 



Inch. 



= A +0.159 



Inch. 



0.072 (A 29.G72) + 0.0005 ( T 75. 8). 



To show the result by the formula in extreme cases, the following eight com 

 parisons are here inserted. 



Inch. Inch. 



Difference. 



No. 3) 

 r Lowest temp. 



&quot; 32) 

 &quot; 46 J 



&quot; 23) 



r . - Greatest pressure 



6) 

 7) 



Least pressure 



These differences prove a sufficient approximation in the terms of the above 

 expression, and likewise leave no doubt that the indications of the aneroid may 

 generally be relied on to nearly within one-hundredth of an inch. 



To facilitate the reduction, the following table of corrections has been calculated 



according to the above formula: 



