1915] Michael, et al. : Hydrocji-aph ic Records of Scriirps Institution 11 



was therefore effected whereby they could be temporarily used for 

 horizontal sub-surface towing:. This was done by employing two ropes, 

 one being tied into the ring supporting the net and the other to the 

 trip-cord. The net, being weighted so as to assume a horizontal posi- 

 tion, was lowered and raised by means of the rope attached to the trip- 

 cord, which thus being taut kept the net closed. After lowering to the 

 desired depth the trip-cord rope was allowed to sag while the rope 

 tied into the ring was made taut and tied. The motion of the net 

 through the water caused it to open and thus a horizontal closing-net 

 liaul was made. This method, however, was very awkward and in- 

 volved such a quantity of rope that it became impossible to make hauls 

 below one hundred fathoms. Moreover, the depth error was so large 

 that hauls could be made with satisfaction only wlieu the sea was 

 very quiet. 



(c) The Kofoiil closing-tut. — This net was put into commission 

 June 21, 1908. It is operated in much the same manner as the Nansen 

 nets, although its great weight requires the large %-inch cable and 

 makes the handling more difficult and quite impo.ssible in rough 

 weather. Being constructed to make horizontal instead of vertical 

 hauls, two messengers are ased, the first to open and the second to 

 close the net. Owing to its weight, the net tends to act as a sea-anchor 

 which, while insuring a great accuracy in depth, makes it necessary to 

 steam ahead slowly with one engine while making the catch. For 

 a full description of this net see Kofoid, 1911a. 



(rf) The sub-surface pump. — During 1903 a pumping outfit was 

 used for collecting microplankton from below the surface. This con- 

 sisted of a semi-rotary clock pump of half-inch intake fitted to one 

 hundred fathoms of half-inch white rubber hose. The hose was in 

 fifty-foot sections connected together with screw couplings. It was 

 lowered and raised by means of an improvised drum operated by 

 hand. The water thus obtained was filtered through filter-paper, no. 

 20 or no. 12 netting or, after settling, it was decanted. Pumping 

 was usually continued for five minutes when, if working at full 

 capacity (eight liters per minute), forty liters of water would have 

 been obtained. The small volume of water thus obtained, however, 

 made the results unsatisfactory, and. after a thorough trial, the method 

 was discontinued. 



(e) The Kofoid water bottle. — This bottle, having a capacity of 

 20 liters, has been used for making microplankton collections as well 

 as for obtaining water samples (see Kofoid, 1905 ; for improved model 



