REPORT OP THE FISH AND GAME COMMISSION. 



129 



were devised for use in mining operations, but with some changes and 

 improvements have been adapted for use with lampblack. 



The Oliver filter, the most expensive and complicated, has proved the 

 least satisfactory. One of this type is in operation at the Metropolitan 

 plant of the Pacific Gas and Electric Company in San Francisco, and in 

 Los Angeles, but it is unlikely that any future installations will be made. 



Fig. 77. Superior type of straw filter of the Pacific Gas and 

 Electric Company at Vallejo. Photograph by A. M. 

 Fairfield. 



The Kelley filter has passed the experimental trial successfully and a 

 battery of three of the largest size has been ordered for use at Station 

 "B" in Oakland. The cost will be $29,100. 



The Butters filter has so far proved the most effective and economical 

 device. Its low first cost, the economy of its maintenance, and its 

 ability to discharge water absolutely free from lampblack, added to the 

 fact that it can be made in any size from a unit of one or two leaves 

 up to any number needed to handle the maximum lampblack output of 

 any plant, makes it by far the most effective and popular installation. 



