i68 The Control of Mosquitoes 



Oil may also be applied by using a garden 

 watering can; this method is useful where a very 

 heavy layer of oil is desired, and where the places 

 to be treated are accessible. 



In oiling shallow waters inaccessible from the 

 shore, a fiat bottomed boat with an oil tank may 

 be used. The boat may be propelled by a small 

 motor, or by hand, and may have a motor or 

 hand-driven pump. A spray nozzle of the type 

 shown is very useful, and saves time. 



Two and four-wheel horse carts of special 

 design are used on the Canal Zone for applying 

 oil. The carts were designed by Mr. H. R. Trask, 

 an inspector in the sanitary service of the Canal 

 Zone. They consist of iron tanks, holding two 

 hundred to five hundred gallons of oil, moiuited on 

 stutable wagon gear. To the lower sides of the 

 tanks are attached three-inch pipes leading to a 

 transverse pipe mounted in front, at the feet of the 

 driver. This pipe is ten feet long, and the outer- 

 most three feet of it is perforated with three rows 

 of one-eighth-inch holes set an inch apart. The 

 pipe is mounted with a universal joint, and is 

 controlled by a leather-operated valve. It is 

 raised and lowered by a pedal. In addition, each 

 cart is provided with a large valve at the back, for 

 withdrawing the oil. 



