- ON SOME POINTS IN THE METEOROLOGY OF BOMBAY. 45 
That exceptions should be found to this state of things in particular loca- 
lities in the temperate zone was far from being improbable; it could not be 
expected that the influences of temperature should always be so simple and 
direct as they appeared to be at Toronto; and a more complex aspect of the 
phznomena might particularly be looked for, where’a juxtaposition should 
exist of columns of air resting on surfaces differently affected by heat (as 
those of land and sea), and possessing different retaining and radiating pro- 
perties. In such localities within the tropics, the well-known regular occur- 
rence of land and sea breezes for many months of the year made it obvious 
that a double progression in the diurnal variation of the force of the wind 
must exist, and rendered it highly probable that a double progression of the 
gaseous pressure would also be found. It was therefore with great pleasure 
that I received, through the kindness of Dr. Buist, a copy of the monthly 
abstracts of the two-hourly meteorological observations, made under that 
gentleman’s superintendence at the observatory at Bombay in the year 1843 ; 
accompanied by a copy of his meteorological report for that year, possessing 
a particular value, in the full account which it gives of the periodical varia- 
tions of the wind, and in the means which it thereby affords of explaining 
the diurnal variation of the gaseous pressure. This pressure presents at 
Bombay an aspect at first sight more complex thah at the three above-named 
stations in the temperate zone, but I believe it to be equally traceable to va- 
riations of the temperature, and to furnish a probable type of the variations 
at intertropical stations similarly circumstaiiced in regard to the vicinity of 
the sea. _ weet 
The observatory at Bombay is situated on the island of Colabah, in N. lat. 
18° 54! and E. long. 72° 50! at an elevation of thirty-five feet above the level 
of the sea. In the copy of the observations received from Dr. Buist, the 
nonthly abstracts are given separately for each month, of the standard ther- 
mometer,—of the wet thermometer, and of its depression below the dry,—and 
of the barometer. In Table I. I have brought in one view the thermometrical 
and barometrical means at every second hour; and the mean tension of the 
vapour and méan gaseous pressure at the same hours. The tension of the 
vapour at the several observation hours has been coniputed from the monthly 
means, at the same hours, of the wet thermometer and of its depression 
below the dry thermometer. The valiies are consequently somewhat less 
than they would have been, had. the tension been computed from each indi- 
vidual observation of the wet and dry thermometers, and had the mean of 
the tensions thus obtained been taken as the value corresponding to the hour. 
The difference is however 80 small, that for the present purpose it may be 
regarded as quite insignificant. It would not aniount in a single instance to 
the hundredth part of an inch; and as in every instancé the difference would 
be in the same direction, the relative values, which are those with which we 
Catherinenbourg, Barnaoul and Nertchinsk, in the ‘ Annuaire Magnétique et Météorologique 
de Russie,’ we find that at Catherinenbourg in that year the barometer exhibits a double pro- 
gression, but that the morning maximum, which occurs at the observation hour of 8" 22™ a.m., 
exceeds the antecedent minimum only by a quantity less thai 0°003 in. At Barnaoul there is 
also a double progression in the barometric mean in that year, the morning maximum being 
still small, and taking place between the observation hours of 95 54™ and 10554" a.m, At 
perecansl also there is a morning maximum occurring at the observation hour of 9° 17" a.m. 
n all the three cases the double progression shown by the barometer disappears wholly in 
the curve of the dry air, which curve exhibits at these three stations, as well as at Toronto, 
Prague and Greenwich, but one maximum and one minimum in the twenty-four hours. At 
the three stations of extreme dryness cited by M. Dove, therefore the vapour was still suffi- 
cient to impart, in the year 1842 at least, a double progression to the diurnal variation of the 
barometer; but the hour of the morning maximum was earlier than where the increase of 
__-vapour, as the day advances, is greater. 
