424 
DE. T. E. EO BINS ON ON THE EEDUCTION OE ANEMOGEAMS. 
Formula where 5=30° and a= 15°. 
6A =(d—d'j cos 15+ (d—d'j cos 45 + (d~ d^ cos 75. 
60=^+^ sinl5+^+<^ sin 45 + ^+^ sin 75. 
6B= {5+5— /s+sHcos 30. 
t 1 6 \3 4/ J 
6P=^- js — S + S — 5 1 +5 — 5. 
I- 1 6 3 4 -1 2 5 
6C= {d-d- (d-d+d-d ) } cos 45. 
6R= | d-\-d-{-d-\-d— (d-\-d^ j sin 45. 
6D=4{5 + S + 5+5] — (s+s). 
L 1 6 3 4 J \ 2 5/ 
6S= { s—s— ( s—s ) 1 cos 30°. 
U 6 \3 4 /J 
6E=(<Z-d) sin 15° — (d — d^ cos 45°+ (d-d} cos 15°. 
6T= p+^ cos 15° - (d+dj cos 45 + (d+dj sin 15. 
12U=5— s— Is— 5\+5— 5. 
1 6 \2 5/ 3 4 
G, for reasons already given, cannot be determined. 
It is, however, necessary to obviate two difficulties which interfere in the present- 
instance with the accuracy of this process, but which do not affect the horary interpo- 
lation. It supposes that the ms employed represent values of the coordinates belonging 
to dates which correspond with a series of <p in arithmetical progression. 
This is not the case ; for (1) the means of each month do not represent exactly the 
coordinates belonging to the middle of that month; and (2) the angles representing the 
distance of the middle of each month from the beginning of each year are not in arith 
metrical progression, as is evident from the following Table, which gives these angles 
=4', and also those belonging to each half month=</,. 
Table VII. 
Month. 
+ 
M- 
Month. 
fi. 
January 
February 
March 
April 
May 
June 
15 16-5 
44 21*2 
73 25-9 
103 25-2 
133 33-6 
163 37-2 
15 16*8 
13 53-4 
15 16-8 
14 46-6 
15 16-8 
14 46-6 
July 
August 
September 
October 
November 
December 
193 40-8 
224 13-8 
254 18-0 
284 24*6 
314 25-2 
344 28-8 
15 16-8 
15 16-8 
14 46’6 
15 16-8 
14 46*6 
15 1 6-8 
Both these difficulties are overcome by a process based on a suggestion of Professor 
Stokes. 
