14 



THE VESSEL, THE APPARATUSES AND THEIR APPLICATION. 



Paying out when trawling on very small depths was made without assistance of the steam- 

 engine, the cogwheel of the main-shaft could namely, by means of an apparatus for throwing out of 

 gear, be put out of connection with the cogwheel of the crank-shaft, so that the large drum was at 

 liberty to revolve and the paying out to be regulated by means of a brake-strap acting on the large 

 drum. When trawling on great depths, where the weight of the wire rope that had been paid out 

 was considerable, the paying out was effected by backing the engine. 



Fig. 7. Trawl-boom. 



By means of a counter worked by the main-shaft, the length of the trawl-wire that had been 

 paid out, could be read, indicated in Danish fathoms. 



Soundings were taken with the vessel lying head to wind. At the same time as the depth, 

 the temperature of the water at the bottom was ascertained, and samples of the water at the bottom 

 were taken. To this end a thermometer and a water-bottle were attached to the hemp stray-line of 

 the lead-line. 



To take samples of the bottom was used Baily's tube, which was generally let down 

 attached to the trawl-frame. 



