INTRODUCTORY ESSAY. 247 



mountains to the north-east are considerably more elevated 

 than those to the northward, over which the aerial current 

 probably flows into the valley of Assam. 



The first condensation of the moisture-laden winds takes 

 place in the lower part of the valley, which is hemmed in by 

 hills at the apex of its delta. Further north there are no 

 more considerable elevations till we reach the sources of the 

 Irawadi, so that in the central part of its course the rain-fall 

 is comparatively small. We have therefore in Pegu a climate 

 like that of the Gangetic delta, the rain-faU amounting at 

 Rangoon to 85 inches ; but in Ava a dry climate, like that of 

 the Gangetic valley, or the Carnatic, prevails, with a moderate 

 rain-fall at one season only. The upper valley is again more 

 humid, from the loftier mountains and the more irregular 

 surface of the country. 



In the delta of the Irawadi there is a maritime vegetation 

 of mangroves, Sonneratia, Heritiera, Excmcaria, and other 

 saline plants, just as in similar salt-marshes along the coasts of 

 the tropics. Throughout the plains of Pegu the vegetation 

 is like that of the Gangetic delta, or the open parts of the 

 valley of Assam. Cocoa-nut, Corypha, and Borassus are the 

 common palms, with Pandanus, Stravadium, and abundance 

 of epiphytical Orchideee. On the mountains the flora is of 

 course more varied, and is a continuation of that of Tenas- 

 serim to the south. 



In Ava, with a climate and temperature very similar to that 

 of the Carnatic, we find an almost identical vegetation. Cap- 

 paridea are common, with acacias, an arboreous Euphorbia, 

 Calotropis gigantea, Guilandina Bonduc, Zizyphus, and Bom- 

 bax ; mangos and Fici, with Borassus, are cultivated. Teak 

 is common on the mountains. The vegetation of the higher 

 parts of the Irawadi is described by Griffith as very similar to 

 that of Assam. 



The valley of Manipur is drained by the most westerly 

 tributary of the Irawadi : it is separated from Cachar by a 

 mountain range, which is 6000 or 8000 feet high, and is 



