154 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Had the smaller size of engine (6i by 8) been used, as I recommended, 

 this diiSciilty would have been avoided, but the Engineer of the Edi- 

 son Company, fearing a possibility of our permitting the pressur*^ to 

 fall below 20 i)ounds, and the engine consequently failing to develop 

 the required power, i)referred to give us this large engine, even at a 

 greater cost to his Company. The Edison Company furnished drawings 

 for the setting of the engine and its foundation, which design I followed 

 implicitly. The plant is so installed as to bring the driving side of the 

 belt on top, so that the slack falls from the pulleys. This results in 

 slipping, particularly as the belt stretches, and when the arc lamps are 

 thrown in circuit the belt slips and the dynamo often slows down from 



Fig. 2. 



1,200 to 1,000 revolutions per minute. I procured a heavier belt, but 

 the stretch soon permitted slipping. I then had a tightener put in. 

 This has been of great assistance to us, but it augments the stretching 

 of the belts very much. I have resorted to doubling the belts, i. c. 

 running one belt on top of the other; this has diminished the slip- 

 l)ing, but the belts tend to separate and run off in ojiposite directions ; 

 to prevent this we have improvised guides. During the year the main 

 valve of the dynamo engine broke — probably from water in the chest — 

 and deprived us of the use of the i^lant about five days. With this 

 exception the plant has been in operation every night when there was 

 steam in the boilers. 



The dynamo (Fig. 3) has given but little trouble. The armature has 

 worn somewhat, and six brushes have been worn away during the year. 

 A spare armature has been i^urchased and is ready for use in event of 



