The Meteoi'ology of the Plains 



[Apkil 



The instruments were compared with those of Captain Herbert and 

 of Mens. Jacquernont, when these gentlemen passed through Sahar- 

 unpore, and subsequently with those of my friend Mr. James Prinsep, 

 on my arrival in Calcutta, and the differences between all were very 

 slight. 



As much of the vegetation of India is of a tropical nature, and as 

 this is found extending into higher latitudes, or to considerable eleva- 

 tions, when local circumstances favour the production of a similar cli- 

 mate, we may therefore notice the characteristics of tropical climate, 

 which consist in great uniformity of temperature, as well as of moisture, 

 throughout the year. Various attempts have been made to ascertain 

 hj calculation the mean temperature of the Equator, assisted by the 

 few observations which we possessed, of places in its vicinity. The 

 illustrious Humboldt was induced to adopt 81° 5' as the mean tempera- 

 ture of the Equator. Mr. Atkinson, on the contrary, inferred, that it 

 •was at least 84° 53' ; but when it is considered that five-sixths of this 

 line passes over the Ocean, the mean temperature of which between 

 the limits of 3° N. and 3° S. varies, in general, between 80"* 24' and 

 82° 4', and as the air which vests upon these waters is from 1° 8' to 

 2° 7' cooler, it is probable that 81^ 5' is not too low for the mean 

 temperature of the Equator. Sir David Brewster, indeed, from obser- 

 vations since made in Ceylon, Penang, and at Singapore, is inclined to 

 think that this may be too high. 



The seasons in equatorial regions are well known to be characteriz- 

 ed by great equability of temperature, and, in fact, they are not 

 distinguished, as in high latitudes, into hot and cold, but into wet and 

 dry seasons, and are greatly regulated by the periodical winds. In 

 Java and Sumatra the thermometer seldom rises above 85° or 90° on 

 the coast, falling as low as 70° at sunrise. The heaviest rains take place 

 in December and January, the driest weather occurs in July and August, 

 while the intermediate months afford variable weather. Singapore, 

 from its insular nature, and being 1° 15' North of the Equator, 

 and near the S. extremity of the Malayan Peninsula, is well suited to 

 give an idea of an Equatorial climate ; there we have, fortunately, 

 therraometric observations carried on for six years by Capt. C. E. Davis, 

 three times a-day : at 6 a. m., 6 p. m., and at Noon (v. Journ. As. Soc. 

 2, p. 428), though the mean temperature deduced from them may pro- 

 bably be a little too high ; but in the whole time the Thermometer 

 never rose above 89°, or sunk below 7i°, and the mean temperature de- 

 duced from the means of the extremes is 80' 04' in all the vears. 



