54 THE ESTIMATE OF THE COST 



their work distributed fairly and evenly. The usual 

 pay of such men can be found out by application to 

 any large employment contractor or agency. 



The cost of the oil likely to be required per year 

 will thus be known, and also the cost of labour and 

 the necessary staff. It only remains to estimate the 

 price of one oil cart for each gang, overalls for the 

 men, and to make allowance for repairs, and for sick- 

 ness among the foremen, etc. 



In this way exact estimates for an urban mosquito 

 campaign should be drawn up. If there are many 

 constant rain-water puddles in which the water com- 

 monly remains stagnant for more than a week, and 

 these cannot be readily drained or filled up, provision 

 must be made in the estimates for dealing with them 

 regularly, like other permanent water collections. 

 Mosquitos require at least twelve days in water to 

 pass their larval metamorphosis even in the hottest 

 weather, and the mosquito larvae will not stand dry- 

 ing ; this knowledge must always be borne in mind 

 when the question of collections of rain-water is being 

 dealt with. 



As stated before, this method of making the esti- 

 mate is not a very great undertaking ; and there is 

 the satisfaction of knowing that it is correct, and 

 that there will be little likelihood of the necessity for 

 subsequent requests for further grants. If there is 

 any doubt on this point it is better to make an 

 estimate in excess, for constant demands for supple- 

 mentary credits are always a source of annoyance to 

 administrators and councils. 



