422 
DR. T. R. ROBINSON ON THE REDUCTION OF ANEMOGRAMS. 
Table IY. 
Hours . 
February . 
• March . 
Normal . 
Triplet . 
Normal . 
Triplet . 
m 
m 
m 
m 
0 
0-07 
0-02 
0-02 
0-00 
1 
0-22 
0-26 
0-02 
- 0-20 
2 
- 0-03 
0-04 
- 0-07 
- 0-12 
3 
- 0-11 
- 0-04 
- 0-07 
- 0-06 
4 
- 0-02 
0-08 
- 0-11 
0-16 
5 
- 0'03 
0-02 
- 0-18 
0-29 
6 
0-21 
0-17 
— 0-07 
0-04 
7 
- 0-17 
- 0-18 
0-01 
- 0-30 
8 
o-oo 
0-08 
- 0-30 
- 0-52 
9 
- 0-24 
- 0-23 
0-01 
- 0-15 
10 
0-11 
0-25 
0-38 
0-57 
11 
0-21 
0-28 
- 0-48 
- 0-29 
12 
- 0-28 
- 0-26 
— 0-02 
0-15 
13 
0-04 
0-00 
0-21 
0-15 
14 
0*01 
- 0-08 
- 0-17 
- 0-32 
15 
- 0-12 
- 0-25 
0-28 
0-31 
16 
0-34 
0-38 
- 0-20 
- 0-01 
17 
- 0-23 
- 0-13 
0-05 
0-01 
18 
- 0-11 
0-11 
— 0"05 
- 0-05 
19 
. 0-07 
0-15 
0-16 
- 0-03 
20 
0-07 
0-19 
— 0-05 
- 0-06 
21 
0*00 
- 0-06 
- 0-09 
- 0-08 
22 
0-11 
- 0-03 
- 0-07 
- 0-17 
23 
- 0-25 
- 0*26 
0-06 
- 0-22 
PE 
+ 0-110 
+ 0-123 
+ 0-123 
+ 0-161 
The triplet combinations are not much inferior to the others, and might possibly be 
sufficient ; but I prefer the latter. Even in the extreme cases of February 16 and 
March 8, 10 h and ll h , the discordance is not as great as I anticipated from the absence 
of the constant S. I tried them, omitting the terms of the fourth order, but the results 
were decidedly inferior. 
In considering the magnitude of some of these errors, it must be remembered that 
the formula expresses only that part of the coordinates which is periodic ; and they are 
the residues of other effects which do not depend on the time 0 , and which disappear 
from a larger series of observations ; for the other hours the errors are much smaller. 
I thought of grouping the hours in pairs, which would probably have given a better 
result than the triple combination; but on deducing the formula, I found it would 
require more logarithmic work than the complete process. In it the coefficient of a 
constant of the order has the coefficient = 6 cospxl5°, instead of- 6, as is evident 
from what precedes. 
