PARK SANITATION 883 



sist of a box or can with a spigot or opening so arranged that the oil will 

 run out continuously, drop by drop. They need frequent attention, and the 

 stream must be kept free from obstructions to allow an uninterrupted spread 

 of oil. Continuous application of oil can also be obtained by soaking a 

 sack of sawdust in oil and anchoring it below the surface of the water. 

 Kerosene, fuel oil and crude oil have been used for mosquito control. Kero- 

 sene is open to the objection that it is expensive, evaporates quickly and 

 lacks color to indicate whether the film is complete. Crude oil, mixed with 

 kerosene, combines the advantage of high toxic power, good spreading 

 ability, gives a lasting film and is easy to spray. Some fuel oils have all 

 these qualities without the addition of kerosene. Waste crank-case oil 

 obtained gratis from garages has been used extensively. 



In California, Mr. H. J. Quayle has used a combination of heavy oil 

 of eighteen degrees gravity, and a light of thirty-four degrees gravity, in 

 the proportion of four to one, respectively. This mixture made an oil just 

 thin enough to spray well from an ordinary spray nozzle and yet thick 

 enough to withstand rapid evaporation. It was applied by a barrel pump 

 where this could be used and by an ordinary knapsack pump in other 

 regions. A single application was found to be effective sometimes up to 

 four weeks. The army of occupation in Cuba used oil every two weeks, and 

 this is found to be about the general practice. 



Larvicides. Paris green mixed with ordinary roadside dust and sprinkled 

 on the surface of the water has been found effective in destroying the Anoph- 

 eles larvae. Two level teaspoonfuls of Paris green mixed with a quart of 

 road dust will be sufficient to treat one thousand square feet of water. 

 Handfuls of the mixture are thrown over the water, preferably with the 

 wind at the distributor's back, and an even distribution will result. Anoph- 

 eles control by weekly application of Paris green is one of the most econom- 

 ical methods that has been discovered, but it must be borne in mind that 

 it is effective against Anopheles larvae only. Other species are not harmed, 

 nor are Anopheles pupae. 



Creosote and various compounds of creosote can be sprayed on water 

 with good effect. It is of particular value where there is enough current to 

 prevent an effective film of oil. Observation will be necessary to make sure 

 that a sufficient amount of the larvicide is being applied. 



Niter cake, a waste product of fertilizer factories, may also be used, 

 particularly in barrels for fire protection. Two pounds of the dry cake to 

 the barrel will prevent breeding for the season. Where it can be obtained 

 in large quantities without cost, it has been dumped into the catch basins 

 of storm sewers with the effect of preventing breeding throughout the storm 

 sewer system. It must be used with care, however, as it varies in strength, 



