14 BULLETIN 18 8, UNITED STATES NATIONAL MUSEUM 



border and the Gulf of Siam, taking in a part of the central plain 

 as drained by the Petchaburi and Pran Kivers. Western Thailand, 

 if it is necessary to recognize this division, might more properly and 

 conveniently be regarded as the mountainous region between Northern 

 Siam and Peninsular Siam extending along the Thailand-Burmese 

 frontier and involving the headwaters of the Meklong, Petchaburi, 

 and Pran Rivers. 



Of the major aflSuents of the Menam Chao Phya in Northern Thai- 

 land the Meping is the most western, rising in the Den Lao Range and 

 having among its tributaries the Mechom, the Mechem, the Mewang, 

 and the Meklang, the last-named stream draining Doi Angka, the 

 highest mountain in the country. The Meyom, and the Menan rising 

 in the Pi Pan Nam Mountains, drain a large part of the eastern sec- 

 tion of Northern Siam. 



Entering the Mekong along its short course where it forms part of 

 the boundary between Thailand and French Laos, there are two note- 

 worthy streams, the Meing and the Mekok, which taking rise respec- 

 tively in the Pi Pan Nam Mountains and in the Khun Tan and Den 

 Lao Ranges, drain wide, level, sometimes swampy districts before en- 

 tering the great parent river. The Mekok has as a principal tributary 

 the Mefang, which in turn has the Memao as one of its branches. 



Central Thailand is the comprehensive designation for the vast 

 plain watered by the Menam Chao Phya and its tributaries and collat- 

 erals, by the lower Meklong, by the lower Petchaburi and Pran, and by 

 the Bangpakong and its affluents the Nakon, Nayok, the Sakeo, and the 

 Prachin. Flowing into the Menam Chao Phya at its head at Pak- 

 nampo and constituting its chief sources are the Meping and the Me- 

 nan, the latter joined near its mouth by the Meyom. Discharging into 

 the Menam near its mouth is the celebrated Bung Borapet, which has 

 been converted into a permanent lake by the construction of barriers 

 and has been set aside by the government as a fish nursery and sanctu- 

 ary. Coming into the Menam Chao Phya from the northwest is a 

 stream known as the Mewong, which rises in the Tanon Tong Chai 

 Range and is the principal western tributary of the Chao Phya. Lower 

 down, about 50 kilometers south of Paknampo and 200 kilometers 

 from the Gulf of Siam, the Chao Phya splits into a number of large 

 streams and forms a delta. The main river divides and reunites, its 

 principal divisions being the Menam Yai, Menam Noi, and Menam 

 Lopburi, which coming together in the region of Ayuthia and joined 

 by a great eastern tributary, the Menam Pasak, flow past Bangkok and 

 enter the Gulf of Siam as a mighty stream whose freshness and silt 

 and mud are carried far into the sea. The other main part of the 

 Chao Phya, beginning as the Menam Supan and changing into the 

 Menam Nakon Chaisi, becomes the Menam Tachin and enters the Gulf 

 of Siam about 40 kilometers west of the Chao Phya. 



