the eastward and southward the neighbouring buildings either obstruct the free passage of the air, or from their low roofs reflect a considerable portion of heat. In comparison with other houses within the fort, those on the western face have many advantages of situation; two of them, exposure, particularly to the sea breezes and the coolness derived therefrom, materially connected with the objects of inquiry. Therefore to establish any positive medium of the climate of Bombay, similar observations made in the country, and some more unexposed part of the fort, are necessary. The thermometers were suspended against a wall two feet in thickness, within a few inches of the angle formed by the junction of another wall of nearly equal thickness; the room itself spacious and lofty. They cannot at any time have been raised by the action of the sun upon them; the walls prevent such an effect, and on the other sides it is even less possible. On these sides also they have not been exposed to any improper influence or current of the air; on one, being sheltered by a door which, being kept open, forms a channel for the air from the other. The height at which the instruments were suspended is about 23 feet above the level of high-water mark.

On the whole the position may be reckoned a favourable one; and this description of it, though detailed, may not, perhaps, be unnecessarily introduced.

In order to render the series of observations more connected, and to bring it at a view under the eye, charts similar to those used by Mr. Playfair in his Commercial and Political Atlas have been adopted; and this mode of conveying information on this subject may possibly, in some respects, be preferable to those hitherto in general use. It affords strong and marked lines, which in the other must be sought and procured only by considerable examination; it also presents an immediate, easy, and fair comparison between any two years or parts of the same year.

The charts No. 1 and 2 exhibit the variations of the thermometer in the years 1803 and 1804: in explanation of them a few words may be requisite.

The charts are divided by lines running from left to right, each space

representing a degree upon the thermometer; the divisions made by the lines drawn from top to bottom represent weeks, which are again above marked off into months.

Upon these the height of the thermometer in the morning and at midday is marked; each daily rise or fall of the mercury being noted by a correspondent ascending or descending stroke, terminating on the line of degrees, or at half or quarter distance between any two of them. When the mercury rose to the same height, or was equally depressed, for several days at any of the times of observation, the straight line is continued until the first deviation; sometimes being so for four or five days. The greatest daily heat, either at noon or afterwards, is thus described, and marked by a red line prolonged to the year's end; the morning heat is similarly shown by a yellow line. The heat at night has not been given, as being between the other two it would have prevented either from being sufficiently clear; but of course by using charts of a larger scale, it may without injury to the other parts be introduced.

The chart No. 3 contains an abstract of the midday or afternoon heat (whenever greatest) of the two years computed from the average of weeks, and is divided by lines representing months; it not only gives a comparison of any two months, but conveys an idea, as far as one can be safely formed on an average of two years, of the midday temperature. Such lines, if contrasted in the same manner with years past, would either prove in some measure that the climate has been subject to alteration, or, if they agreed, would give the certain mean midday temperature of each month.

The heat at noon or afterwards, when greatest, has been alone attended to in this last chart, not only as that by which we are most materially affected, but as showing the power of the sun and the great influence which it has upon the remainder of the day, in proportion to its duration and extent. It will be at once observed that the difference between the height of the mercury at noon, and at morn or night, is very trifling during the monsoon, when we are usually protected from the rays of the sun.

To have given a line taken from the average of the three daily observations would have been easy; but the difference between the heat at noon

and morning (when the mercury is lowest) may be easily seen, either by reference to the charts 1 and 2, or to the following table.

Average monthly difference between the greatest heat at noon, and

Greatest difference in the heat of the day at any time within each month.

In estimating the mean temperature of the island from the averages of all the observations, the following result is obtained:

This medium appears to be a more favourable one, than from observations in other parts of India, or of the world in the same parallel of latitude, we should have been warranted in supposing.

The above mode of framing a general average, although a common one, is liable to several objections; it certainly does not procure a just and fair conclusion; and however correct the principles may be when applied to other subjects, they do not equally extend to this. For instance, take 79° as the general average of the morning heat in 1804, contrast this with the chart, using the correspondent line as the means of comparison, and it will be found that of 366 observations, but twelve will agree with it: it cannot therefore convey an accurate idea of the morning temperature. The monsoons, periodical and generally prevalent winds, have been by many qualified persons already treated of so fully, that nothing worth attention could be extracted from the diary on these points; but the following table of the number of rainy days in each year may be in some small degree interesting, particularly as they happened to be years so opposite in the great leading feature; the first of unusual scarcity, the second of uncommon abundance.