192 MOSQUITOES 



making larger holes and filling them with wicking or oakum, 

 through wliieh the oil would filter slowly. Any such method, 

 however, would probably meet some difficulties through the 

 abundant dirty residue which such oil always contains, but I am 

 very sure that such experiments would result in a method of 

 automatic distribution of the oil from such anchored barrels. If 

 the water is deep enough they could be sunk with stones, and 

 with holes on the upper and lower sides, the oil would press up- 

 ward by the difference in specific gravity and tlius give a con- 

 stant pressure on which to issue slowly. 



Mr. Matheson's experience at Lloyd's Neck did not 

 fully coincide wdtli that of Mr. Kerr in regard to the 

 durability of the surface-film. He states that his experi- 

 ments with oil upon a five-acre pond indicated that the 

 fuel oil would maintain a film for about a week, while the 

 ordinary illuminating- oil, with which he first experi- 

 mented, would last only half that time, the light fuel oil 

 being very much heavier in gravity than the illuminating 

 oil. The periods for which the film persisted varied ac- 

 cording to the weather. With a high northw^esterly wind 

 the film w^as broken and the oil driven on the lee shore. 

 He believes that an application every twenty days would 

 be perfectly effective, but the cost of a more frequent ap- 

 plication was so slight that he did not care to take the 

 chances and treated the pond mentioned about every two 

 weeks. 



Persons who are reading up on th mosquito question 

 will naturally consult the works of the English and Ital- 

 ian investigators, and it may be well to suggest that the 

 word *' kerosene " apparently does not occur in the Eng- 



