MALARIA EXPEDITION TO THE GAMBIA 
37 
out of the drains at the close of the wet season would be helpful for the purpose of 
removal of the small pools of water which collect in some parts of the bed of the drain. 
Special care ought also to be taken to provide for the entrance of fish, which have 
been shown to be such excellent mosquito scavengers. The centrally situated grass- 
clogged drains ought to be abolished ; as drains they are inefficient, and as they form 
the chief source of mosquitoes in Bathurst at certain times of the year, they urgently 
require attention ; many of them could be got rid of by filling in with the earth and 
sand piled up on either side of these drains. Their place should be taken by superficial 
saucer-shaped drains. The filling in of these drains will take some little time, and it 
will be necessary to adopt some method in the meantime to prevent, or at least to 
diminish, the numerous mosquito larvae infesting them. The only feasible way will 
be the employment of labourers to keep the drains free from long grass and rubbish, 
and the intelligent application of kerosine. Also special attention should be taken to 
keep the mouths of these drains free from rubbish, so that small fish can gain easy 
entrance to them. 
Natural Breeding-Places. The abolition of the breeding-places occurring in the 
swampy districts of Bathurst is a work which will take some time, and consists 
practically of raising the level of the swamps by the deposition of sand, together with 
a proper system of drainage. At Half Die swamp the process of filling in was being 
pursued with great rapidity during my stay at Bathurst, and a great portion of this 
area has been raised two or three feet ; still there is a large area of a swampy nature 
in Bathurst to be treated in this manner, and until this is accomplished it will be 
necessary to provide some other method of ridding these districts of mosquito breeding- 
places. In this connexion, it must be remembered that mosquitoes do not breed in the 
central mass of water in the swamps, this water being disturbed by winds, the rise 
and fall of the tide (to some extent), and, also, it is well stocked with fish, so the 
mosquito breeding-places to be dealt with will be found along the borders of this 
water, and will vary in position according to the height of the water in the swamp. 
Mention has been made of the holes, irregularities, ditches, and large pools which 
occur on the borders of the swamps (chiefly Box Bar swamp), and in which it was 
shown mosquitoes bred in great quantities. Such-like breeding-places could be dealt 
with by filling them up with sand — the number of them is not very great ; around the 
borders of Box Bar, for instance, there are only about fifteen of the larger holes to be 
dealt with. This work could easily be accomplished during the dry season by a few 
labourers. During the rains special inspection should be made of the borders of the 
swamps, and the breeding-places found treated with kerosine or other oil ; I believe 
that the application of kerosine in an intelligent manner would produce some good 
results, nor do I think the cost would be very great. In the streets bordering on the 
swamps, holes and irregularities occur, but more especially are they found in the native 
compounds in these situations, and in the rainy season, when the swamp water is high, 
