282 REV. R. BARON ON THE 
and are therefore less impenetrable, than those on the eastern 
side of the island. 
'The country is drained by numerous rivers, of which the Sofia, 
Betsiboka, Manambolo, Tsiribihina, Kitombo (or Mangoky), and 
Onilahy, all of which take their rise in the mountains of the 
interior, are the largest. As for the geology of the country, the 
rocks apparently belong almost entirely to the secondary forma- 
tions, and chiefly to the Jurassic and Cretaceous series; indeed 
the eastern boundary of the Region almost coincides with the 
limit of the sedimentary strata. As a rule these strata have been 
but little disturbed and, roughly speaking, have a very slight dip 
towards the west coast. "They consist chiefly of sandstone and 
limestone, with beds of shale and clay. 
The heat is much greater in the western than in the eastern 
part of the island, but what the temperature may actually be is 
at present unknown. In the north-west of the island in the 
month of November I have seen the mercury rise to 140? Fahr. 
in the sun ; but asthis was the highest figure on the thermometer, 
the actual heat was probably greater. In regard to the tempe- 
rature of the south-western portion of the island, the Rev. A. 
‘Walen says :—“ In the so-called rainy season the heat on the 
south-west coast is most intense and, in the middle of the day, is 
almost unbearable." 
Very little also is known in regard to the rainfall of the 
Region, no record, so far as I am aware, ever having been kept. 
But there can be no doubt that there is much less rain in 
Western than in Eastern Madagascar, the moisture brought by 
the south-east trade-winds being almost entirely absorbed by the 
eastern mountains. Mr. Walen says :—“ The soil of the country 
is fertile, but on account of the very small rainfall during the 
rainy season (there are frequently long droughts), it produces 
very often but little return to an agriculturist, being liable to 
failure of crops and years of scarcity. During the two years I 
spent on the coast there was scarcely any difference in the rain- 
fall between the rainy and the dry seasons. The rain was very 
scarce indeed all the year round. Only slight showers occasion- 
ally fell in both seasons of the year, varied by some few heavy 
squalls from the north-west ...... The rainy season (from 
October to March) is also the hurricane season. As to the 
amount of rain there is a great difference between the east coast 
and the west coast, the former of which gets a superabundance 
