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are generally much more numerous in small pools. Now, 

 it is evidently bad economy to spend large sums over 

 draining large bodies of water, when small puddles, easily 

 dealt with, really cause more mischief. The superintendent 

 must suppose nothing he must never suppose, because a 

 marsh exists in the neighbourhood, that it is the only or 

 the principal cause of the malaria. He must study the 

 point by careful search for Anopheles' larvae ; and may often 

 find that a small unobserved pool in the street is more 

 dangerous than a marsh a mile away. 



The number and nature of the breeding pools depend 

 so much on the configuration of the ground, the character 

 of the soil, and the amount of the rainfall, that it is impos- 

 sible to give very minute directions regarding the method 

 of dealing with them. The superintendent must be guided 

 by his own judgment, remembering only the maxim, which 

 applies to most kinds of work : The simplest measures first. 

 Some general advice may, however, be useful. 



Small Pools. Wayside ditches, which have been simply 

 dug out in soft soil, and have become full of pools in con- 

 sequence of silting, require alternate filling and cutting so 

 as to be converted into a channel of uniform calibre and fall. 

 Where the obstructions are caused by rock, this must be cut 

 through by means of the pickaxe or jumper. A channel 

 six inches square in section is enough to drain most roads 

 where water does not come down from above. Turf or 

 stamped rubble are good for binding the edges of such a 

 channel cut in soft earth. Vegetation in the course o the 

 channels should be cleared, but not on the banks. A)ols 

 formed in depressions or flat surfaces of soft soil should be 

 filled with rubble, gravel, or earth. When they are con- 

 tained by outcrops of rock, the latter must be cut through 



