376 Ei. L. DeForest on Correcting an error 
r,4-4¢ 
1 cf 
Mya [yde=A+Be, +0(2? a): 
t,—$e 
Substituting in this expression for M, the values of A, B, C, 
already found, and reducing, and putting / for the time in days 
rom tke beginning of the middle calendar month to the begin- 
ning of the mean month, / being negative when the latter begins 
earlier than the former, and employing H, K, L, as auxiliary 
letters, we obtain the following series of equations by which to 
find the value of M,: 
1 
ny=l4s(e—ng), 
H=(n,-+c)(".—c) — 122 2, 
M,=m,+(K+L)m,—Km,—Lm,. 
Now taking those values for n,,n,, 2,, and h, which are appro- 
priate for each of the twelve months in succession, allowing 
284 days to February, and giving ¢ its value of 30,5 days, we 
shall find that 
M, =m, +0036 m,- +:0029 m,.—"0065 m, 
M, =m, —'0123 m, —-0028 m, +0151 mg 
M, =m, +0027 m, —-0237 mz, +0210 m, 
M, =m, —:0041 m, —'0190 m, +0231 m, 
M, =m, +°0015 m, —-0207 m, +0192 m, 
M, =m, —'0038 m, —:0171 m, +°0209 mz 
M; =m, +°0025 m, —-0190 mg +°0165 mg 
M, =m, +°0024 m, —'0098 m, +0074 my 
Ms =m, —-0026 m, —-0064 m, +0090 my, 
1019 +'0029 m,,—0081 mg +°0052 m,, 
12—=, 20032 m,.—-0062 m, , +0030 m, 
These twelve equations make it easy to compute the mean tem- 
perature, M,, of any one of the twelve mean months when the 
mean temperatures, m m My4,, of the three nearest calen- 
nm 1) ™ ? . 
dar months are known. And it may be remarked that this 
used it for computing the “agate of the curve for Greenwich, 
and compared the result with that obtained: by the hel of the 
table of daily means. It gives the means for mean months thus: 
