154 JAS. J. SIMPSON — ENTOMOLOGICAL 



remembered that troops are frequently transferred backwards and forwards 

 between these two places. 



From these facts, it will be evident that, from the point of view of the subject 

 in hand, the sanitary conditions in Freetown merit serious consideration in 

 connection with the possibilities of the spread of insect-borne protozoal diseases. 



From Freetown a railway runs nearly due east for a distance of about 230 

 miles, nearly to the Liberian frontier, while a branch railway extends 

 northwards from Boia Junction, about 65 miles from Freetown, through 

 Ronietta, Roruks and Makump, where it crosses the Rokell River. 



The only other port of call for ocean-going steamers in Sierra Leone is 

 Bonthe, on Sherbro' Island ; but this is visited only by intermediate and cargo 

 steamers, and its importance entomologically will be discussed at greater length 

 in the general narrative. 



The configuration of the Protectorate varies much in the different localities. 

 The parts on the banks of the rivers are, for the most part, low and swampy, 

 while away from the rivers the country consists of low rolling downs, with here 

 and there a range of hills rising to a height of about 3,000 feet. The country is 

 well watered by rivers and streams, and is on the whole fertile. 



(2.) Vegetation. 



It is almost impossible to describe in any general way the distribution of the 

 various zones of afforestation found in Sierra Leone. I have elsewhere* given 

 in greater detail the nature and composition of the various types of forests, and 

 the following classification must, therefore, be taken in conjunction with what 

 was stated there. 



As a general rule, it may be said that the type of forest found in any locality 

 depends greatly on the length and duration of the wet and dry seasons 

 respectively, and on the intensity of the rainfall ; but the conditions in Sierra 

 Leone have been seriously altered by extensive felling and cidtivation on the 

 part of the native. Consequently, the extent of the primeval forest and of the 

 types of vegetation which follow its destruction depends greatly on the density 

 of the population in the various parts. 



The forest growths of Sierra Leone may be divided into : — (a) tropical rain 

 forests, (b) savannah forests, (c) fresh-water swamp forests, (d) fringing forests 

 and (e) mangrove forests. 



It will be noted that there are no monsoon forests ; this type of vegetation is 

 associated with a fairly porous soil and a distinct differentiation of wet and dry 

 seasons, with the latter more in evidence — a combination of factors not to be 

 found in Sierra Leone. 



At one time the whole of Sierra Leone must have been covered by tropica* 

 rain forests, but for the reasons given above, this type is now confined to the 

 tops of mountains and a few isolated portions of the Protectorate. In addition 



* Bulletin of Entomological Research, Vol. III., p. 143. 



