93 



A.funestus was found near but not in Freetown. 



In my opinion, already your efforts have been crowned with a 

 large degree of success, as there has been a noteworthy diminution in 

 the number of the first two genera found in the houses. The number 

 of breeding grounds has been enormously diminished. 



The operations, having been only recently begun, are, of course, as 

 yet far from complete. A considerable part of the town, perhaps half, 

 has not been touched. Even in the parts longest under treatment, in 

 the yards adjoining the streets, there are still numerous breeding 

 grounds ; and in the streets themselves occasional places have either 

 been overlooked or the works undertaken have not been effective as 

 yet. 



The breeding places dealt with could be only of importance in the 

 peculiar circumstances of Freetown, *>., where the soil is impervious 

 and the rainfall excessive (no in. to 200 in.). Even in Freetown most 

 of them would be destroyed by a week's dry weather, and some by 

 less. As, however, the wet season in Sierra Leone is a prolonged one, 

 for this place these breeding grounds are of great importance, and in 

 dealing with them an excellent beginning has been made. 



A great part of the work will not be permanent. The rock cuttings 

 are too narrow, many of them being blocked after each shower. The 

 earth cuttings are also very liable to fall in. This results in much 

 extra work and supervision, as considerable supervision and labour is 

 required, constantly, to keep the work already done in order. 



I suggest that during the dry season the rock cuttings should be 

 broadened, so as to be at least three inches at the bottom, the sides 

 being inclined at about 60. When the rush of water is greater a 

 broader cutting will be requisite.* 



The earth cuttings should in all cases have sloping sides where 

 possible, as this minimises the liability to formation of pools, and 

 ensures, even with a small amount of water, a persistent current. 

 There are few things more suitable for Anopheles breeding grounds 

 than a drainage system in which the water supply is insufficient to 

 flush the drains. 



The plan adopted of placing large stones at the edge of the 

 channel, blocked behind by smaller ones, will, I think, suffice if the 

 work is strengthened with cement ; but brick drains would be prefer- 

 able in my opinion, as they are easier to clear. 



* Exact uniformity is not essential, but an approximation to it will save a 

 large amount of labour in clearing the channels ; and as this requires to be done 

 very frequently, the point is of importance. 



