NARRATIVE OF THE CRUISE. 



65 



When all the instruments had been attached to the line it was eased down 400 or 

 500 fathoms by being passed round the drum of the donkey-engine, which was fitted 

 with a break for this purpose. When that amount of line had been eased out it was 

 allowed to descend freely, the ship being kept exactly over the spot where the sinkers 

 entered the water. As the line ran out the exact time each 100 fathom mark entered 

 the water was registered and entered in its appropriate column in a book provided 

 for that purpose, and the interval between these times was calculated and entered in 

 another column. These intervals gradually increase in length as the depth increases, the 

 sinkers being retarded in their descent by the friction of the line as it passes through the 

 water, which increases with the amount of line paid out ; they will, however, be found 

 to increase in regular proportion as long as the sinkers are descending, but directly they 

 reach the bottom there will be a sudden lengthening of these intervals, as then only 



Table showing the Mean Bate of Descent of Sounding Lines with Weights 



of 3 and 4 cwt. attached. 



(nark. CHALL. EXP. — VOL. I. — 1884.) 



