196 



DISCOVERY REPORTS 



proved unsatisfactory. It frequently slipped and it is almost certain that a simpler 

 pattern, with two screws at most, would prove more efficient. 



If a large net is lowered rapidly there is a tendency for both net and closing mechanism 

 to slide up the warp, and if this happens the lines by which the messengers for the lower 

 net are attached will break: it is also very likely that when the apparatus slides back 

 to the stop the momentum consequent upon the impact will be sufficient to effect 

 release. This possibility was foreseen when the apparatus was designed, and room is 

 made for the insertion of a small stop / at the upper end to prevent any movement 

 in an upward direction. The primary messenger is shown at m and the secondary 



Fig. 20. Opening and closing mechanism for large horizontal nets, shown in use. 



at n: the former is $\ lb. in weight and stream-lined in form, the latter is 22 lb. in 

 weight and apart from the conical extension piece is similar in shape. The smaller 

 messenger travels at a rate of 3^-47 min. and the larger at about 4-5 min. per 1000 m., 

 the speed depending largely on the angle of the warp. The entire apparatus is made 

 of phosphor bronze except for certain pins, at points where exceptional strength is 

 required, which are of steel. 



Apart from the defects shown in the stop this apparatus proved all that could be 

 desired, but as is explained further on, the results obtained with these large horizontal 

 nets were not always satisfactory. 



Depth Gauges. To determine with any accuracy the depth at which mid-water nets 

 are being towed is a matter of some difficulty. In most deep-water investigations the data 

 on this point appear to be based mainly on guess-work, and in a recent expedition all 

 attempts to determine the level are abandoned, and the only information given regarding 



