64 



tow-nettings should be taken as frequently as possible. 

 All such observations on the floating life of the sea 

 (which includes the eggs and the microscopic food of 

 many fishes) are most useful. Occasional hauls at par- 

 ticular seasons with a large mid-water net to ascertain 

 the presence of larvre and young fish would be most useful, 

 but might form a part of the additional exploration work. 

 III. Physical Observations. — (a) Sea Temperatures. — 

 Surface and bottom observations should be taken at the 

 beginning and end of each drag, and should be read to 

 0'1° C. Bottom temperatures should be taken with a 

 reversing thermometer. At certain stations in deep water, 

 periodically, serial temperatures at 0, 2, 5, 10, 15, 20, 25, 

 30, 40, 50, 60, and 70 fathoms should be taken. 



(b) Specific Gravity (density) of the Sea Water. — Sur- 

 face and bottom observations should be taken at the 

 beginning and end of each drag, and should be read to 

 the fourth place of decimals. Bottom observations 

 should be made on samples of the bottom water, taken 

 with a Mill's bottle. The temperature and specific 

 gravity should be taken simultaneously in the same 

 sample of water. A sample (at least one litre) of the 

 sea water should also be kept and sealed up in a stoppered 

 bottle for examination of the salinity in the laboratory. 



(c) Air Temperature. — One observation at the begin- 

 ning of each drag should be taken for comparison with the 

 sea temperature. 



(d) Barometric Pressure. — One observation taken at the 

 beginning of each drag is sufficient. 



(e) Transparency and Colour of the Sea Water. — One 

 observation should be taken at the beginning of each drag, 

 and if any notable change has taken place in the water 

 a second observation should be made at the end. 



(/■) Currents. — Drift bottles and other weighted floats 



