6 
ME. F. CHAMBEES ON THE DIITENAL VAEIATIONS 
more salient features. The smoothed curve has been calculated from the original one 
by means of the- first three terms of Bessel’s formula. It clearly exhibits a double 
period like the north and south variation and like the barometer variation, and (remem- 
bering that no attempt has been made to eliminate the portion of the land- and sea-breeze 
which probably still remains) its general resemblance when inverted to the barometer- 
curve (fig. 2) is very remarkable. The part of this variation which contains the double 
period, and which will be supposed independent of the land- and sea-breeze, will here- 
after be called the longitudinal diurnal variation of the wind, to distinguish it from the 
whole east and west movement given in Table I., and from the pure land- and sea-breeze. 
6. If we again make the same assumption as before, regarding the nature of the land- 
and sea-breeze, viz. that its direction is completely represented by the line A B (fig. 1), 
its effect in modifying the north and south double diurnal variation of the wind may be 
approximately eliminated by measuring the north and south components from the line 
A B as the datum line, instead of from the east and west line. This has been done by 
means of the expression 
North component of double diurnal wind variation — north component of whole wind 
variation as given in Table I. + tan 184° X east component of whole wind variation 
as given in Table I., (4) 
and the following variation obtained, which will hereafter be called the meridional 
diurnal variation of the wind, to distinguish it from the whole north and south movement 
given in Table I., and from that part of it which belongs to the land- and sea-breeze. 
Table IV. — Meridional Diurnal Variation of the Velocity of the Wind at Bombay. 
Bombay Civil Hours 
0 to 1. 
1-2. 
2-3. 
o-4. 
4-5. 
5-6. 
6-7. 
00 
1 
K 
Velocity in miles perl 
hour J 
0-44 s. 
0-23 s. 
0-24 s. 
0 09 n. 
0'45 n. 
0-64 n. 
0-62 n. 
0-47 n. 
Bombay Civil Hours 
8-9. 
9-10. 
10t-11. 
11-12. 
12-13. 
13-14. 
14-15. 
15-16. 
Velocity, in miles perl 
hour J 
0- 13 n. 
0 03 s. 
•102 s. 
1*53 s. 
1-63 s. 
1-70 s. 
107 s. 
0 40 s. 
Bombay Civil Hours 
16-17. 
17-18. 
18-19. 
19-20. 
20-21. 
21-22. 
22-23. 
23-0. 
Velocity in miles per 1 
hour J 
0-48 n. 
O 97 n. 
1-54 n. 
1-61 N. 
100 N. 
0-36 n. 
0-10 s. 
0-37 s. 
This variation is also graphically represented by fig. 8. Its value of course depends 
on the correctness of the assumption as to the nature of the land- and sea-breeze, which 
maybe only approximately true, and the variation may therefore be subject to correction 
hereafter when the exact nature of the land- and sea-breeze becomes known. 
7. It will be observed that the great distinguishing feature of the diurnal variation 
of the barometer, viz. the double period, is the most prominent one in the meridional 
