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184. The engineers being unduly optimistic regarding the influence their prospective drainage system would have on the mosquito population at first refrained from carrying out the medical authorities' recommendations for screening the lines. Later, the large catches of mosquitoes in the lines having proved the need for such protection, attempts were made to remedy the error but with only partial success.
135. Such screening had however one advantage for it converted the lines into traps where such mosquitoes as did find entrance had difficulty in escaping. The trapped insects were caught by the catcher in the morning. Specimens of species which normally leave the proximity of their host after partaking of his blood, and which would otherwise have escaped, remained behind on the screens to be added to the catcher's bag for subsequent dissection. In this way faulty screening assisted the Malariologist in his investigations.
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136. Researches carried out in the Malaria Bureau had proved A. jeyporiensis, which breeds in the wet terraced fields among the hills, to be a very potent carrier. What was not known in 1933 was its range of flight. This was afterwards proved to exceed half a mile, a matter of great importance to Shing Mun Camp which had, within flying distance, a large number of such fields some under rice cultivation, others abandoned and permanently flooded, the latter being even more dangerous than the former.
137. The population of the Camp varied between 1875 in January and 2835 in November. The average monthly labour force was 1974 as compared with 595 in 1933. Most of these were Cantonese but there was a considerable force of coolies from Shanghai and a few Tamils, natives of South India. In addition there were between twenty and thirty Europeans occupying properly screened bungalows a quarter of a mile distant.
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138. As will be seen from the map the Camp lies close to the divide separating the waters running east to the Shing Mun from those running west and south to empty into Gin Drinker's Bay.
139. The Shing Mun River rises east of Tai Mo Shan, flows south to Pineapple Pass afterwards turning east to enter the gorge. Above the gorge the bed of the river is strewn with granite boulders and pebbles of various sizes, the stream itself consisting of pools connected by small rapids. It finally outlets into Tidal Cove near Shatin.