156 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



struction of the nearest cut-out plug:, thus preventing damage to the 

 wire; in such cases I have added insulation to the wires to prevent a 

 repetition of the accident. 



A few lamp sockets (Fig. 4.) have burut out — principally from arcing 

 — and a few h{j,ve been broken by accident. I have provided myself 

 with a number of the various-sized screws used in these sockets and 



Fig. 5. 



have been able to repair them myself. The arc lamp has destroyed 

 two of these sockets, probably by arcing through the socket as the cir- 

 cuit was opened or closed. For this reason I have substituted two key 

 sockets (Fig. 4.) for two ordinary sockets at points where the arc lamps 

 were attached, and am now making a special attachment which I think 

 will eliminate this difficulty. 



Fig, 6. 



The safety plugs, shown in perspective in Figs. 5 and 6, and in sec- 

 tion in Fig. 7, have answered their purpose admirably. The piece of 

 solder {a, Fig. 6.) melts at a lower temi)erature than the wires, and is 

 destroyed in event of a low resistance short circuit on the wires. 



Fig. 7. 



I have never known one of them to fail. When one of these safety 

 l^lugs melts it breaks the circuit, and the lamps on that section are im- 

 mediately extinguished. After discovering and reijairiug the damage, 

 the circuit is restored by substituting a new plug in the cut-out block. 



Fig. 8. 



By indicating the engine I find the economy to be practically uniform. 



