134 



ginning of the season to determine the exact date of the initial oiling. 

 Thereafter oiling should be done at intervals not greater than two weeks 

 or less than ten days, according to the time of the season. 



The next portion of the experiment was the comparison of the efficiency 

 of sprinkling-can and the air-pressure sprayer (fig. 17). 



Figure No. i shows the position of the sprinkling-can and the flow of the 

 oil. The objectionable features of this ^method of oiling are as follows: 



1. The position of the can to enter and leave the intake of the basin was 

 such as to allow oil ^ to flow into the gutter of the street. Considering there 

 are 3,600 basins in Newark, and that there should be at least eight applica- 

 tions per season, the amount of oil thus wasted was quite appreciable. 



2. The actual area of the surface of the water covered by the falling oil 

 was about one-third of the area of the entire surface of the water in the 

 basin. The remaining two-thirds were covered merely by the oil tending to 

 spread over the surface. Any rubbish floating on the surface would, there- 

 fore, have kept the water from being completely covered. 



3. The can holds not quite two gallons of oil. 



Figure No. 2 shows the position of the air-pressure sprayer. The salient 

 features of it are as follows : 



1. It holds three gallons of oil. 



2. After pumping the air chamber full of air, all that remains to be done 

 is to insert the pipe and press on valve A (Fig. No. 2), which releases the 

 air pressure, forcing out two cone-shaped sprays as shown. 



3. The entire surface of the water is reached immediately. 



4. The film of oil is uniform. 



5. There is no waste oil. 



One hundred basins were oiled by each method and a time study miade, 

 with the following results: 



In using the sprayer only two applications were used, and it is very prob- 

 able that three should be used. This would make 5.82 gallons of oil needed. 

 The difference in the amount of oil saved is so great that it seems to me, 

 even though the time be the same, the latter method is preferable. It must 

 be remembered that the above time does not represent the amount of time 

 it would take to spray one hundred average basins in the county. It merely 

 gives us a comparison of the times of the two different methods. To get 

 a fair average of the number of basins that could be oiled in one day, it 

 would be necessary to spray all the basins and divide the time by the 

 number. This is due to the various locations of the basins. 



At the conclusion of these two experiments a sewer-basin was flushed 

 continuously for one-half hour after a filmi of oil was placed on its surface. 



Observations showed that the oil was confined strictly to the edges of 

 basin during the flushing. When the flushing had ceased the oil immediately 

 flowed back over the surface of the water, and, as near as I could ascertain, 



Method. 

 Sprinkling Pot 

 Sprayer 



Time. 



46 Minutes 



47 Minutes 



Oil 

 18.25 gals. 

 3.88 gals. 



