15G On the Statistics of Didhun. [Jan. 



the barometer and thermometer; but there were curious approximations. 

 The extreme dewing points differed 32°. The dewing point has been as 

 high as 76°, temperature of the air 79°, a cubic foot of air containing 10'049 

 grains of aqueous vapour •, but this is a rare occurrence. An instance 

 occurred of the dewing point being obtained at 3° below the point of the 

 congelation of water, the temperature of the air being 62°, and a cubic 

 foot of air holding 2" 146 grains of water. There is also an instance of a 

 dewing point, in February, 1828, being 61° below the temperature of the 

 air, VIZ., from 90° to 29°, but I nerer afterwards succeeded in determin- 

 ing anything like so great a depression. 



In January, 1827, there was a range of the dewing point of 38°, and 

 the extreme range of the year was 47°, viz., from 29"^, temperature 62°, 

 in January, to 76°, temperature 79°, in June. In 1829, the mean dew- 

 ing point for the monsoon was 69° -62, temperature 75°-83; the cubic 

 foot of air containing 8*191 grains of water. In 1830, the observations, 

 are only complete for 9—10 a. m. ; the mean dewing point was 61 °-9. 

 temperature 78°'4, and a cubic foot of air contained 6'35l grains of wa- 

 ter; the extreme range of the hygrometer was 47°, the lowest dewing 

 point 31°, temperature 50°, in December. It might be supposed that 

 the hottest months in the year, March, April, and May, would also be 

 the driest; but such is not the fact. The powerful action of the sun on 

 the ocean, in the middle of March, raises a large quantity of aqueous 

 vapour, which continues to increase in the ratio of the sun's progress 

 north: the westerly winds waft this vapour into Dukhun; much of it is 

 arrested by the Ghats and hilly tracts eastward of these mountains: ac- 

 counting for the sensible moistness of the air, the frequent night fogs, 

 and deposition of dew in this line, in the end of March, and in all April 

 and May. The supply of moistiu'e diminishes in proportion to the dis- 

 tance eastward from the sea, to the limits of the Coromandel coast mon- 

 soon. We in consequence find the Ghats, Poona, Ahmednuggur, and 

 the Bala Ghat, all with very different dewing points in the hot months. 



The hygrometric state of the air in Bombay and Dukhun is remarka- 

 bly contrasted : in fact, there is more aqueous vapour suspended in the 

 air in Bombay in the hot months, than there is at Poona at any time 

 during the monsoon. In April and May, 1826, in Bombay, the monthly 

 mean dewing points were respectively 72°-84 and 75°'59, temperature 

 83°-48 and 84°-52, a cubic foot of air holding 8-988 grains, and 9-743 

 grains of water suspended ; whilst Jul)^, the most rainy month during 

 the monsoon, at Poona, had only a mean of 8-775 grains of water sus- 

 pended. In 1827, the means of ten days' observations in Bombay, in 

 April, gave 10*243 grains of aqueous vapour in a cubic foot of air: and 



