394 The Philippine Journal of Science 1921 
water from its source, had a great influence upon the salty na- 
ture of the Tachin. According to Graham, 5 
From Paknampoh to the sea, 140 miles as the crow flies, the waters of the 
Menam Chao Phaya follow a number of tortuous courses. At Chainat, 
about 35 miles below Paknampoh, it throws off on the west side a branch 
known as the Suphan or Tachin river, which flows parallel with the 
parent stream to the sea. 
The Nakorn Chaisri district is in the southern part of the 
central division of Siam. This division is characterized by being 
a vast plain of about 14,245,000 hectares (55,000 square miles), 
stretching from the mountainous border of Burma and extending 
eastward to the high ridges marking the boundary of Cambodia. 
The plain extends southward to the Gulf of Siam. According 
to Graham, 6 
The plain lies at a very slight elevation above the sea and is subject to 
regular annual river floods which, by the deposition of vast quantities of 
silt, are slowly raising the general level. The whole area has a gentle 
slope downwards from north to south and the land falls slightly away 
at right angles to the banks of the rivers which flow on slight ridges 
of their own alluvial accumulation. There is abundant evidence that 
within recent geological times the sea flowed over a great part of the plain 
and even now the northern shores of the gulf are advancing seawards at 
the surprising rate of almost a foot a year. 
The Nakorn Chaisri section is in the delta region of the Me- 
nam Chao Phaya. In this region, according to Graham, 
The waters usually begin to rise in May and continue to do so until 
about the end of October, when the river is in full flood. Subsidence is 
gradual and the lowest level is reached about April. Sudden freshets 
and high rises are unknown in the Menam Chao Phaya. 
The river is subject to a strong tidal influence for a distance 
of 80 kilometers inland. The action of the tide is greatly in- 
fluenced by the flood time, depending upon the rainy and dry 
seasons of the year. During dry weather the tidal flow extends 
far inland and in the lower parts of the river the water is 
brackish. 
CLIMATE 
TEMPERATURE 
Graham gives the climate of Siam to be as follows : 7 
5 Graham, W. A., Siam. A Handbook of Practical Commercial and Polit- 
ical Information. London (1912) 16. 
" Op. cit. 8. 
’Op. cit. 31-32. 
