I04 DISCOVERY REPORTS 



The old pattern of deep sea hammer with the unbalanced head was in use with the 

 oceanic machine until 1935, and although requiring constant attention and adjustment, 

 gave good results; but during the running survey of the South Shetland Group in 

 1934-5 it gave trouble continuously and was practically rebuilt on board. These repairs, 

 however, were only of a temporary character and it was replaced by a new hammer of 

 the balanced type during the refit in London in August 1935. 



The 'Acadia' pattern recorder fitted in 1933 gives excellent results, the proved range 

 during the third commission being from 20 to 2800 fathoms. Trouble, however, was 

 experienced with the high tension batteries and the special paper. This paper is wetted 

 by an endless wick dipped in a tank of water, and complete saturation is necessary as 

 electrical contact must be made from the travelling pen through the paper to the tank 

 face before the sounding can be recorded. The 'starving' of the paper may result 

 from its uneven texture, or it may be caused by the wick becoming choked with fluff 

 and chemicals which rub off the paper as it ' feeds ' over the wick. To correct the latter 

 fault the wick can be removed and boiled, but in the former case nothing can 

 be done except to try a new roll of paper. This difficulty has been overcome in the 

 Mark XII machine by using pre-saturated paper supplied in sealed containers and fed 

 directly over a roller to the tank face instead of over a wick. 



The battery trouble was more serious but was easily remedied. It was found almost 

 impossible to maintain the H.T. batteries at a working voltage as they were seriously 

 affected by the cold and damp. This was due to the door of the echo-cabinet, which 

 is also an entrance to the chart house, being left open for long periods. As a correct 

 H.T. voltage is absolutely necessary to produce a good record, and as it was impossible 

 to have sufficient spare batteries, it was decided to replace them by accumulators. 

 These were already in existence on board for the direction finding apparatus, and as 

 the lead to the latter runs through the echo-cabinet, it was a simple matter to fit an 

 extra switch and lead to the recorder. The charging board for these batteries is in the 

 chart house, so there is no difficulty in keeping the battery charged to full capacity. 

 When the Mark XII recorder was fitted in 1935, Messrs Hughes approved this machine 

 being run from the same battery and a special switch has been fitted which allows either 

 recorder or the direction finder to be used separately. 



LABORATORY METHODS 



Methods of sorting, preserving and storing specimens are similar to those described 

 in vol. I, pp. 216-20, except that all the jars used are now of the Kilner pattern — with 

 glass lid, rubber washer and copper ferrule. Two new sizes have been added : one is the 

 wide-necked 7-lb. jar which is useful for large specimens and heavy catches of plankton, 

 and the other is the ^-Ib. size used almost exclusively for plankton samples from the 

 vertical 70 and 50 cm. nets. Formerly these samples were preserved in tubes, and there 

 was some inconvenience in reducing the samples sufficiently to get them into the tubes. 

 The catch can be poured straight into a i-lb. jar from the plankton bucket or settling 



