emulsion is of secondary importance in solving the conservation problem. 

 Some of the samples of oil extracts in water used in this work were 

 examined under a microscope at the magnification x625* The samples of 

 extract were not opalescent and contained no oil globules* After 

 centrifuging a small amount of sediment was collected. It consisted 

 of iriwgularly shaped, emgular black particles apparently derived fran 

 crude oil. Furthermore, in ihe tests using oil held by carbonized sand, 

 shaking and agitation was completely eliminated, yet the water slowly 

 running over the layer of the mixture had a definite toxic effect on 

 marine animals . 



Oil placed on clean water will spread to a thickness of one molecule. 

 This ultimate result may not be reached if the surface tension of the water 

 is lowered by the presence of other contaminating substances. There is a 

 definite relation between the thickness of the oil films, their appearance, 

 and the quern tity of oil required to produce them. It is known that a 

 trace of irridescent color may be observed in an oil film of an approximate 

 thickness of 0.000006 inch. A film of that type is produced by 100 

 gallons of oil spread over one scfuare mile of sea surface. Smaller 

 quantities of oil produce beu-ely visible films, the thinnest one, 

 visible only tmder most favorable light conditions, corresponds to 25 

 gallons of oil per one 8qu«a*e mile of area. Films of dark dull color 

 are about •00008 inches thick. They require about 1, 332 gallons or 

 more per square mile. The American Petroleum Institute (1933) puts 

 much emphasis on the fact that thin oil films are very unstable and 

 even those of the average thickness, of the order of 0*00004 inches, 

 disappe«u* from the surface of the sea in less than 24 hours. On the basis 

 of their data, the American Petroleum Institute infers (1, c, p. 9) "that 

 oil discharged into surface waters at the rate of 666 gallons per day, or 

 28 gallons per hour, per square mile, may not be cumulative under average 

 conditions. This rate would probably result in a continuous irridescent 

 film." This conclusion is based primarily on observations of the dis- 

 appearance of oil slick from the surface of the water but does not take 

 into consideration the fact that, in silt-laden waters, oil is rapidly 

 cctnbined with the suspended material and is loosely deposited on the 

 bottom. Thus, from a biological point of view, the absence of oil frcm 

 the surfaoe of the water does not indicate that the pollution has ceased. 



Oil discharged on the surface of coastal waters, '^ith their complex 

 system of currents, may be carried some distance from the source of 

 original pollution. Ih loose combination with the material suspended in 

 water, it may settle on the bottom, but strong currents, wave action, and 

 storms may stir it up and oil slicks may reappear on the surface and be 

 carried farther with the currents. 



The harmful effect of a submerged oil slick on the bottom-dwelling 

 forms may continue because of the leaching of toxic substances. It is 

 true that under usual conditions in the open bays and estuaries the 

 dilution of the materials leached by sea water would be great, and for 

 this reason the injuriousness of these substances to marine life may not 

 always be observed. A different situation exists, however, in the bays 

 and harbors with slow currents and limited circulation. In such 



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