94 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



speed of the engine is greatly reduced. Two engines are set up ready 

 to connect with the shaft, so that if either one gives out the other may 

 be used. The engines are 2h to 3 horsepower, Fairbanks-Morse 

 vertical type of gasoline explosion engines, and have proved exceed- 

 ingly satisfactory. 



Boxes with filters for holding minute larvce. — As a modification of the 

 usual form of box or car, to be used for rearing larvae so small that 

 they would go through any screen with meshes large enough to permit 

 an adequate renewal of water, the following has been adopted : The 

 ordinary boxes are carefully caulked in all the seams, and their win- 

 dows, save one of those in the bottom, are covered with canvas. A 

 gravel and sand filter, made by putting about 4 inches of gravel and 

 sand into a shallow box with wooden sides and heavy galvanized one- 

 fourth-inch mesh wire in the bottom, is placed over the other bottom 

 window (fig. 13). When the car is in place, an old-fashioned bucket 

 chain is rigged on the longitudinal shaft, and the water is thus con- 

 tinually lifted and poured into the hatching box through a short 

 trough. The buckets are painted with asphalt inside and the trough 

 is lined with canvas to prevent contamination of the water from con- 

 tact with metal or wood. The new water is added, therefore, at the 

 top of the box gradually — about 3^ gallons per minute (figs. 15 

 and 16). 



The amount of water passing through the bottom of the filter does 

 not create an appreciable outward current, and, at any rate, the fry 

 are held above the bottom by the upward trend of the current created 

 by the propellers. Two or three cars of this type have been operated 

 for periods of four to ten weeks at a time. Several varieties of very 

 young fishes and larval invertebrates have been reared with highly 

 satisfactory results. Among the many hundreds of thousands of 

 animals only three or four dead specimens of any kind have been 

 observed. 



Canvas lining for boxes. — ^A further modification of this method has 

 been adopted in order to prevent the escape of certain very small 



