184 MOSQUITOES 



scarcely be pumped ; some were too thick in cliill}^ weather 

 and conkl not be pum^Ded at all, while some w^ere limp, 

 easily handled, made a good uniform coating on the 

 ponds, and were very effective. So long as the oil flows 

 readily and is cheap enough, the end is gained, provided 

 it is not too light and does not evaporate too rapidly. 

 Mr. Matheson, in his North Shore experiments, arrived at 

 the same conclusion, and the petroleum which he found 

 satisfactory for use on the mosquito-breeding ground was 

 that known by the Standard Oil Company as '' light fuel 

 oil." 



In the accounts of the early experiments of the English 

 observers in West Africa, it was found, according to their 

 reports, that the petroleum Avhich they placed upon runs 

 was not persistent, and that it was necessary to renew the 

 application at much more frequent intervals than has been 

 found to be the case in this country. The explanation of 

 this is undoubtedly that some light illuminating oil was 

 used, which was more volatile than was at all necessary, 

 and which at the same time was unnecessarily expensive. 

 The army workers in Cuba have been advised by the 

 writer to use this fuel oil of the Standard Oil Company. 



I am informed by the Standard Oil people that at the 

 time Mr. Kerr's work was being carried on the price of this 

 oil was $2.25 per barrel, but that in March, 1901, the price 

 had advanced and was $3 per barrel, including the barrel, 

 f. o. b.. Point Breeze, Philadelphia, or Bayonne, N. J., an 

 allowance for the barrel to be made upon its return, the 

 allowance, however, depending entirely upon the condi- 

 tion of the barrel when received by the Standard Oil 



