1900.] Capt. L. Rogers — Malaria North of Calcutta, 95 



South Dum Dum is divided into three wards, and one of these 

 which borders on Cossipore, from which many of the people whom I 

 examined were accustomed to get filtered water had only a spleen rate 

 of 11*8, against one of 35'4 and 45*3 in the other two wards which had 

 only tank water, although in all other respects I could find no difference 

 between the wards. The very fact of the people taking the trouble to 

 carry filtered water from a distance, and their robust belief that they 

 to a large extent escape fever by so doing, must be allowed some weight 

 in favour of the correctness of their belief. The whole of the evidence, 

 then, points to the water supply as the determining factor in relation- 

 ship to the relative amount of malaria in this tract of country, but 

 other possible factors must be considered, the most important of which 

 is water-logging. 



Water-Logging and the Railway. 



It has already been pointed out that Maniktolla and Chitpore- 

 Cossipore are the most water-logged parts of the whole area, and yet 

 they are the least malarious, owing to their filtered water supply. 

 Further, an examination of the spleen rate and the ground water level 

 ward by ward shows that there is no relationship between the height 

 of the ground water level and the percentage of inhabitants with large 

 spleens. At first sight the fact that the bank of the Hooghly river 

 is very sl:^,-htly higher than the surrounding country, so that the 

 drainage flows away from the river and eventually finds its way back 

 through khals, or runs into the Great Salt Lake to the East of Calcutta, 

 might appear to indicate that the eastern portions of this area must 

 have a higher ground water level than those near the river bank.. 

 Measurements in the wells, however, do not bear this out, for there is 

 very little difference in this respect, while what little there is is rather 

 more frequently in favour of the eastern portions than against them. 

 Further if different wards of the same municipalities are compared no 

 definite or constant relationship between the slight variations in the 

 ground water level which are met with and the spleen rate is found as 

 a study of the tables in the full paper or the map will show. 



The Eastern Bengal Railway, which runs from north to south 

 through this area, and together with the grand trunk road roughly 

 divides the western and eastern portions, has frequently been held to- 

 be responsible for the unheal thiness of the country, for it lies across 

 the line of drainage. As, however, the drainage flows from west to 

 east it is obvious that if it materially obstructs the drainage the part 

 to the west of its course should be the more unhealthy, while precisely 

 the opposite is the case. Moreover, in places in which wells were 



