104 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. [102] 



As soon as the specimen of ocean soil is removed tlie cup is carefullj' 

 rinsed in water and adjusted for use. 



A small portion of each bottom specimen is preserved in a vial when- 

 evei; we are working on new ground, or if anything unusual is discov- 

 ered, and at the end of each season the specimens thus collected are 

 sent to the laboratory at Washington. 



SERIAL TEMPERATURES AND SPECIFIC GRAVITIES. 



As soon as the wire is in, the wind is brought a trifle on the starboard 

 quarter by stopping the port engine and backing slowly on the star- 

 board, turning ahead on the port if necessary. 



There are two cast-iron sinkers provided for the temperature rope, 

 one 520 and the other 150 pounds weight. One of these is shackled 

 to the end of the dredge roi^e, swung over the side, and lowered a fathom 

 or two under water, to steady it, the boom being rigged in until the rope 

 rests against the side, inclining a little inboard above the rail. 



The vessel having been placed in position, a thermometer and water 

 bottle are sent to the officer of the deck, who clamps them to the tem- 

 perature rope, the former lower down, in order that, in capsizing to 

 register the temi3erature, there will be no danger of its striking the 

 water bottle. The navigator sets the valves of the water bottles, and 

 examines the thermometers before they are sent out. 



The dredging boom is swung out far enough to clear the rope from 

 the ship's side, and 100 fathoms veered, another thermometer and 

 water bottle clamped on, and the operation repeated to 800 fathoms; 

 the next and last 100 fathoms has instruments at 50 and 25 fathoms. 



When sufficient time has elapsed for the thermometer at 25 fathoms 

 to take the temperature the rope is reeled in and the boom swung in as 

 the instruments appear above the rail. The officer of the deck unclamps 

 the thermometer and reads it, then hands it to the record keeper who 

 A^erifies the reading and notes it, as well as the number of the instru- 

 ment, in the record book. The boatswain's mate of the watch unclamps 

 the water bottle and delivers it to the surgeon or apothecary, who dis- 

 poses of it as before mentioned. The instruments are rinsed in fresh 

 water and returned at once to their proper receptacle. 



The process is repeated as each pair of instruments reaches the surface 

 until they are all on board, when the sinker is removed and the trawl 

 shackled to the dredge rope. The rate at which the instruments are 

 lowered and hoisted is from 50 to 75 fathoms per minute, depending 

 somewhat upon the state of the sea. 



It may not be out of place to mention here the care with which the 

 temperatures are read when the deep-sea thermometers are used. It is 

 well known that an error of parallax arising from the thickness of the 

 thermometer tube is liable to occur ; and, in order to reduce it to the 

 minimum, the writer devised a sight block, which is simply a piece of 

 close-grained wood an inch and a half in length, an inch wide, and 



