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MALARIA EXPEDITION TO THE GAMBIA 21 
the drain a cemented catch-pit occurs, one foot in depth ; this I also 
found afforded an excellent place for mosquito larvae. A few other drains 
in a similar condition to the one described above must be specially 
mentioned. Commencing at Government House and running behind 
the Hospital and Telegraph Station is a rather deep drain, which takes the 
water from a small swamp in this region, discharging into Box Bar by 
two smaller drains crossing Clifton Road and running through Portuguese 
Town. In these drains mosquito larvae are very abundant until the end 
of November, and especially was this the case in the two smaller drains. 
One of these small drains crosses Clifton Road at the back of the 
Hospital ; being dug out of pure sand its bed naturally was dammed up 
by the falling in of the sides of the drain. In the dry season for this 
reason also the drain becomes practically obliterated. The other drains 
crossing Clifton Road, nearer the Cemetery, were also converted into a 
series of pools by the falling in of sand and rubbish. On my arrival, and 
up to the end of November, these two drains swarmed with mosquito 
larvae ; from a rough estimation I made during these months I calculated 
that one larva was present in every four square inches ot surface water. 
These two drains were five hundred feet long, and the water in them on 
an average was two feet across. From these data one is able to calculate 
approximately the number of larvae occurring in the drain, and, also, the 
number of mosquitoes issuing into the town per week from them. 
The following are some of the principal streets in which the drains occur : — 
Long Street, Grant Street, New Street, Allan Street, Kent Street, Clarkson 
Street, Dobson Street, Perseverance Street, Prometheus Street, the shore end of 
Buckle Street, Lemon Street, Picton Street, the town end of Lancaster Street, the 
swamp end of Hill Street. 
In some of these streets the earth dug out to form the drain has been piled 
up on either side of it, so that the surface of the street falls away from the drain. 
These grass-overgrown ditches also occur around some of the native compounds in 
New Town, on the south side of Box Bar, on three sides of McCarthy's Square, and 
on either side of Clifton Road, bordering Portuguese Town. These drains are 
certainly to be condemned ; even after heavy rains they appear to allow very little of 
the surface water to pass along them. Dr. Forde informed me that he has observed 
very little current in these drains after a heavy shower, and I have made a similar 
observation. They then collect the rain-water, which stagnates and becomes foul, 
and only disappears when the level of the ground water sinks below the bed of the 
ground, that is about two months after the rains. They have been shown to be often 
