4 
ME. F. CHAMBEES ON THE DIUENAL VARIATIONS 
of 184°, then all the hourly points being projected in a north or south direction upon 
this line will give a series of points which will represent the variation of the land- and 
sea-breeze combined with any of the diurnal variation which may exist in the same 
direction, similar to that which does exist in a north and south direction. The varia- 
tion is given below, and has been obtained by multiplying the east components of the 
variation of the wind for each hour, given in Table I., by secant 18^°. 
Table II. — Mean Land- and Sea-Breeze at Bombay. 
Bombay Civil Hours 
0 to 1. 
1-2. 
2-3. 
3-4. 
4-5. 
5-6. 
6-7. 
7-8. 
Velocity of wind in miles 1 
per hour J 
E.S.E. 
1-89 
E.S.E. 
2 41 
E.S.E. 
2*84 
E.S.E. 
333 
E.S.E. 
3*93 
E.S.E. 
452 
E.S.E. 
5-33 
E.S.E. 
5*68 
Bombay Civil Hours 
8 to 9. 
9-10. 
10-11. 
11-12. 
12-13. 
13-14. 
14-15. 
15-16. 
Velocity of wind in miles 1 
per hour J 
E.S.E. 
5-44 
E.S.E. 
4 31 
E.S.E. 
1*96 
W.N.W. 
092 
W.N.W. 
387 
W.N.W. 
5-42 
W.N.W. 
6-82 
W.N.W. 
710 
Bombay Civil Hours 
16 to 17. 
17-18. 
18-19. 
19-20. 
20-21. 
21-22. 
22-23. 
23-0. 
Velocity of wind in miles j 
per hour J 
W.N.W. 
6 7 6 
W.N.W. 
5-63 
W.N.W. 
3-97 
W.N.W. 
2-26 
W.N.W. 
M3 
W.N.W. 
012 
E.S.E. 
077 
E.S.E. 
1-57 
It is also represented graphically by fig. 6, which will be seen to be remarkably like 
the temperature-curve (fig. 5) in general character, but from about 1 to 2 hours later 
in phase. This general resemblance is satisfactorily explained by the theory already 
adverted to ; for the producing cause of the land- and sea-breeze, according to that theory, 
being the difference of temperature indicated by two temperature-curves, viz. that of the 
land and that of the sea (which presumably differ from each other only in extent and not 
in form), will also be represented by a temperature-curve of a like nature ; and it is to be 
expected therefore that the land- and sea-breeze, when represented as in fig. 6, will have 
some such resemblance to the temperature-curve as that which it exhibits. But fig. 6 
has at the same time very definite and distinctive features peculiar to itself ; amongst 
these may be mentioned : — 
1st. Its rapid transition from east to west, moving from 1T| hours to 12^ hours 
through nearly half of its whole range, which is much more rapid than the corre- 
sponding change of the temperature-curve. 
2nd. From 18 hours to 6 hours the curve is first convex and afterwards slightly 
concave downwards, having a point of inflection about midnight, while the tempe- 
rature-curve is convex downwards during the whole of the same interval. 
These features are what might be expected from the superposition on the land- and 
sea-breeze of an east and west double diurnal variation of the wind which attains its 
maximum east positions at about the same hours at which the barometer reaches its 
