[103] U. S. FISH COMMISSION STKAMER ALBATROSS, 105 



three fourths of au inch thick. A score is cut ou one end which con- 

 forms in shape to the outside of the metal case inclosing the ther- 

 mometer. To read the thermometer (Negretti and Zambra's) hold it at 

 the height of the eye and toward the strongest light. Place the score 

 of the sight block against the metal case, below the point of reading, 

 and raise it carefiiUy until the line of sight corresponds exactly with 

 the upper surface of the block and the top of the column of mercury in 

 the tube, when the temperature may be read with much greater accuracy 

 than could be attained without the block. 



DREDGING OR TRAWLING. 



As soou as the sinker is on board, the port engine is started with a 

 caution to the engineer of the watch to "Go slow for dredging!" 



The vessel will naturally swing to starboard, which she is allowed to 

 do until the intended course is reached, the wind on the starboard bow, 

 or abeam, being the most favorable if it is intended to steam ahead 

 while dredging. 



In the meantime the trawl has been hoisted to the boom end and 

 swung out ready for lowering as soon as the vessel is steadied on her 

 course. It is first landed on the surface of the water and held there 

 until the frame assumes a horizontal position, the net extending aft, at 

 full length, the mud bag floating clear of the bridle ends, and the wing 

 nets towing aft and clear. Then the order is given, "Lower away!" 

 The speed of lowering is regulated by the record keeper, who stands, 

 watch in hand, ready to check or increase the rate of descent, wliich is 

 never allowed to exceed 25 fathoms per minute in depths over 300 

 fathoms. The machinist attending the hoisting engine calls out each 

 100 fathoms, so that the offlcer in charge knows at all times the amount 

 of rope out. 



The port swinging boom is rigged out and towing nets put over as 

 soon as the vessel is steadied on her course, the speed for dredging 

 (about 2 knots per hour) being admirably adapted for surface work. 

 The nets are in charge of a man detailed from the crew, who works 

 under the direction of a naturalist. 



While the trawl is being lowered the officer in charge watches the 

 angle of the rope, regulating the speed to keep it between 30° and 60°. 

 He notes the trend of the rope also, whether it is toward or from the 

 ship, and in the former case changes the course a trifle to starboard, 

 which tends to carry it from the side. It frequently happens that the 

 vessel will not steer with the port engine turning at a speed of 2 knots 

 or less, especially after much rope has been veered out. In this case 

 the starboard engine is started and the port one stopped. There is no 

 difiiculty while the starboard engine is in motion, as the inclination to 

 turn to port is counteracted in a great measure by the drag of the trawl. 

 This engine would be used at all times when steaming ahead were it 



