192 MOSQUITOES 



making larjjjer hoU-s and lilliii;^: tlicm with wicking or oakum, 

 through which tlie oil woulil liltcr slowly. Any such metlKul, 

 however, wcnihl [jrobably meet some ditflculties through the 

 abundant dirty residue which such oil always contains, but 1 am 

 very sure that such experiments would result in a method of 

 automatic distribution of tiie oil from such anchored barrels. If 

 the water is deep enougli 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 thus give a con- 

 stant pressure on which to issue slowly. 



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

 fully coincide with that of Mr. Kerr iu 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 Avould 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 wdiich the film persisted varied ac- 

 cording- to the weather. With a high northwesterly wind 

 the film was 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 the mosquito qiiestion 

 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 Eug- 



