Attack by Oiling 155 



surface flows smoothly, where the channel is fairly 

 free from obstructions and flotsam, and where 

 there is very little vegetation and algas. In a word 

 * ' drips ' ' are most useful where there are few, if any, 

 impediments to the formation of a good unbroken 

 film. An important advantage gained by using 

 oil drips is that oil is transported by the stream, 

 and left in the form of an oil film on the quiet 

 water along the bank where there is little or no 

 current, and where mosquito larvae are most apt to 

 be found. 



Circumstances occasionally arise which call for 

 the installation of a drip on a stream that does not 

 offer the requirements mentioned. For instance, a 

 rapidly moving, tortuous stream may empty into 

 a quiet, wide pond, in which conditions are favor- 

 able to mosquito breeding. This stream may flow 

 close to a road along which oil may be easily 

 transported. The pond may be at an inconvenient 

 distance from the road, and difficult of access for 

 wagon or cart. Under these circumstances, it may 

 be advisable to install a drip on the stream at some 

 point near the road, and by this means carry the 

 oil to the pond, where it is needed. This example 

 shows the possibiUties of utilizing a stream as an 

 oil carrier. Our construction camps were fre- 

 quently situated near sluggish streams or branches 



