5^ 
Report of the malaria expedition. 
more successful ultimate!}-. In the same street many puddles bearing larva; \\ere treated — some with 
kerosene and some with tar. After 24 hours all were free from larva;. After a further interval the 
puddles were again examined ; with the result that all the puddles treated with tar were still free from 
larva;, while many of those treated \vith kerosene contained lar\x'. This result is due to the greater 
evanescence of the kerosene film. 
II. ACCRA. 
RAINFALL AT ACCRA, 1897 
On October i8th I landed at Accra, and after being very kindly received by the Governor of the 
Gold Coast, who spontaneously offered me all the assistance in his power, I was fortunate enough to meet 
Dr. Chalmers, who kindly offered me quarters, and for whose hospitality and assistance in my work I 
cannot too warmly express my gratitude. 
Accra, a straggling town consisting roughly of four parts— native, commercial, official, and 
Christiansborg — {vide Map III.) is situated on a perfectly flat plateau on the coast, about 25 feet above 
sea level. From the level of the town to the sea-shore stretch broken and crumbling rocks ; and on the 
other side, northward of the toun, the countrj- is absolutely flat (save for a slight depression here and 
there) for 26 miles, until the Aburi Hills are reached. 
During my stay at Accra I ivas unable to find an}- puddles, and consequently Anopheles, notwith- 
standing a rigorous search throughout the entire district. To those who know the conditions under 
which Anopheles were found at Sierra Leone this will not be 
surprising, for the conditions at Accra are totally different ; the 
rainfall never exceeds 27 inches per annum, as compared with 170 
inches at Sierra Leone. Again, at Sierra Leone the geological 
formation is volcanic rock, whereas Accra is built on sand and 
gravel ; consequent!}- the small rainfall is ver}- rapidly absorbed b}- 
the porous ground. There are no trees, and therefore there is no 
shade. 
I include here a chart showing the curve of the rainfall 
at Accra.- 
It has been found that the number of fever cases is greatest 
during the second quarter of the year, that is to say, just before, 
during, and just after the period of greatest rainfall {vide chart). 
Another rise in the number of cases occurs in the last quarter ; 
when again it will be noticed that the rainfoU increases. At this 
time too the " Haimattcn " blows, and there is a great fall in the 
temperature at nightfall. The increased liability to chill at this 
time no doubt, to some extent, explains the increase in the number 
of fever cases. I ma}- sa}' that during 1899 the rainfall has been 
somewhat less than usual. 
Not only was I unable to find any specimens of Anopheles 
in Accra, but Dr. Chalmers, an enthusiastic entomologist, also 
had not seen any during the three months prior to my arrival. 
Other kinds of mosquitoes were present without limit ; and I 
seized the opportunity to examine as many of the Culex species as 
possible. Fifty-t\\-o specimens I dissected, but in none did I find 
zygotes. Before deciding that Anopheles is never found at Accra, 
w-e must wait to see if they are present when the rains are at 
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their height, that is to say, in May or June. 
Thc^c being the chief facts \\-hich I obtained as regards the 
losquitocs of Accra, one ^vould 
