816 FE. L. DeForest on Reducing Meteorological Observations. 
ArT. XXXV.—On the Reduction of Meteorological Observations ; 
by Erastus L. DEForsst. 
THE system of twelve equations for correcting monthly means 
for the unequal length of the months, given by me in this Jour- 
nal, vol. xlil, page 155, was obtained on the supposition that the 
year consists of 3654 days. The true length of the year being 
a very little less than this, it follows that the equations referred 
to are not exactly correct. The amount of inaccuracy in their 
results is indeed very small, but still it seems desirable that fun- 
damental formulas of this kind should not involve any unneces- 
resented by the are 30° 33’ 18’-2, a month of 30 days by 29° 
34’ 9-9, and the month of February by 27° 50’ 12'"8. The 
values of x, for the several months are therefore 
anuary, —0° 16’ 391 July, 1° 4’ 536 
February, -+0 31 35 °4 August, O 31 354 
March, 1 19 49 °9 September, 0 27 51°3 
April, 116 58 October, 0 24 7°3 
A 432 2h 7 November, 0 20 23 2 
June, 1: 883% December, 0 16 39°1 
and the twelve equations are found to be 
=m, +°0037 m, +°0030 m,,—°0067 m, 
* 
2 =m, —0127 m, —-0031 m, +0158 m, 
M, =m, +0028 m, —-0249 m, +°0221 m, 
M, =m, —‘0042 m, ~—-0200 m, +-0242 m, 
M, =m, +0016 m, —-0218 m, +0202 m, 
Me =m, —-0039 m, —-0180 m, +0219 m, 
M, =m, +-0026 m, —-0200 m, +0174 mg 
M, =m, +0025 m, —-0103 m, +:0078 mg 
M, =m, —-0027 m, —-0067 m, +0094 my 
Mo=M, +0030 Mo—'0085 m, +°0055 m,, 
11M, ,—"0026 m, , —"0046 m,,+°0072 m,> 
M, 2=m, 20032 m,, —-0064 m™,,+:00382 m, 
It will be seen that the numerical coéfficients here given differ 
from the previous ones to the amount, in some cases, of a single 
unit in the fourth decimal place. They 
exact as they can be made without extending them beyond the 
