'Transactions of the Bombay Geographical Society, from January 1847 to May 1849. Edited by the Secretary. Volume VIII.' [‎15] (30/496)

recur, so far as is known, in all parts of the world from two to three hours before
noon and midnight, and from four to five hours after them, ten minutely readings
from J to 9 to J past 10, and from £ past 3 to 4 past 5 a. m. and p. m., would go
far to determine all that was required to be ascertained. When the approximate
hours of maxima and mimima were known, two observations daily at each of these
would shew the menstrual inequality, if any existed—or perhaps indicate the in
equalities of the year. All the observations of each day, before being of use for
comparison with each other, must be taken on the same spot. Indeed, until the
daily fluctuations of the mercury be determined, all observations made with the
Barometer, on altitude, must prove fallacious where no fixed standard of reference
can be had recourse to. The kind of Barometer should be mentioned, as well as
the maker’s name : and the fact indicated as to whether or not the mercury has
been boiled in the tube.
“ In most parts of the world the temperature at 4 past 9 or 10 o’clock gives the
mean temperature of the day. One set of hourly observations would indicate
whether it was so or not in the regions about to be explored ; and, if so, by the
help of self-registering Thermometers, a single inspection of a pair of instruments
at the proper hour would give the maximum, minimum, the range, and the mean.
At Bombay the mean temperature of September is also the mean of the year, and
should the explorers be out during the month referred to, it might be well carefully
to note its heat. The 9 o’clock observation will probably give the means both of the
month and the year. It is not likely a year will be spent by them in any given
locality; nor is it safe to assume a local law as of universal acceptation ; but we
might put up with this information until better could be procured. Deep springs
and wells will give a close approximation to the mean temperature of the spot
throughout the year, as will a thermometer sunk three or four feet under the sur
face of the ground, and carefully covered over. We are so utterly devoid of all
knowledge of the regions about to be visited, that to ascertain the curvature and
direction of the Isothermal lines would solve an important problem in physical
geography.
“ In case the mission should not be provided with self-registering Thermometers,
or in the event of these being broken, it may be mentioned, though probably well
known to the gentlemen composing it, that a bottle of water or other vessel of con
siderable size, sunk in the earth, with a thermometer enclosed, will in the course
of eight or ten hours acquire the temperature of the surrounding mediae, and will,
if too much time is not lost in removing it, retain its heat long enough to allow the
thermometer to be examined; and will give indications probably within a degree
or so of accuracy.
“ Should other instruments fail, this will give a pretty close approximation of the
altitude of any place in relation to some other in the neighbourhood of which
the mean temperature has been determined.
The humidity of the atmosphere is quite as important a matter in climatology
as its temperature or pressure ; and the Society would strongly recommend the
assiduous use of the wet-bulb thermometer.
“ The tint of the sky, and force of the wind, in these unexplored regions, many of
which attain such stupendous altitudes, would be interesting; and in defect of, or