i64 The Control of Mosquitoes 



much oil must be applied to a given area of water 

 surface. Such an estimate may be made for 

 laboratory work, but it cannot be made for success- 

 ful field application. Many factors operate to 

 make such an estimate difficult : Wind and wave 

 action; presence of vegetation, grass and brush 

 projecting through the water surface or floating on 

 it, and algas; the varying density of the heavier oils, 

 the diverse quaHty of various lots, and the varia- 

 tions in a given lot under differences in tempera- 

 ture. In Panama just enough is applied to attain 

 the desired result. 



Where large quantities of oil are to be used, the 

 first consideration, from a standpoint of economy, 

 is the distribution of the oil from its source to the 

 places where it is to be used. The following meth- 

 ods of distribution were used in Panama. 



About 600,000 gallons of crude oil have been 

 used annually for the sanitary work in the Canal 

 Zone. The oil was brought from California in 

 tank steamers, principally for use as fuel, and the 

 supply for sanitary purposes was obtained from the 

 oil company. The oil steamers discharged their 

 cargo into storage tanks situated at the Pacific 

 Ocean canal terminus. From these tanks it was 

 pumped across the Isthmus of Panama through 

 pipes owned by the oil company. At various 



