GENERAL INTRODUCTION TO THE ZOOLOGICAL REPORTS. 17 



by the stop breaking, or by the line carrying away. Where no accident occurred, when 

 the dredge had been on the bottom for a sufficient time — from an hour and a half to 

 two hours — the rope was brought to the deck-engine, and the dredge brought up. 

 We found that the strain on the line was so great that the men could not hold 

 on to it while it was being hove in, when turns were passed round one drum only 

 of the engine; by the arrangement already described (p. 10), by the time the rope had 

 reached the starboard drum, the pressure was so far relieved that the men could handle it 

 easily, and a great support was given to the bearings of the engine. 



On one or two occasions, when, owing to the great depth (over 3000 fathoms), 

 we could not spare sufficient time to allow the dredge to sink in this manner, we 

 fastened a sounding-rod to the bottom of the dredge-bag or trawl and put 4 cwt. of 

 detaching weights on the rod. The dreclge was then let go perpendicularly, the ship 

 being kept stationary until sufficient line had been paid out to allow the rod to reach 

 the bottom and disengage the weights, when the ship was allowed to drift a little 

 way, and the leads were then attached to the thimble and allowed to slide down the 

 rope to the toggle. This is a very good way of dredging or trawling quickly in deep 

 water. 



In running a section across one of the ocean-basins at the average depth of the ocean 

 — from 2000 to 2500 fathoms — the dredging operations on board the Challenger fell 

 into a regular routine. Steam was got up at daybreak (we had probably been running 

 on under sail all night), and the ship was hove-to during the morning watch and a 

 sounding taken. The exact depth, the nature of the bottom, and the bottom temperature 

 having been thus ascertained, and a sample of the bottom-water procured, the dredge or 

 trawl was put over after breakfast, and the line slowly veered, in the manner described 

 above, to about 4000 fathoms. In from two to three hours the movements of the ac- 

 cumulators indicated that the dredge had reached the bottom, and it was allowed, with all 

 precautions, to drag for an hour or two. The operation of heaving-in then commenced, 

 and continued for four hours or more, according to the resistance from the weight of the 

 dredge or the state of the weather. When the number of 100-fathom marks on board 

 indicated that the dredge was nearing the surface, the naturalists congregated on the 

 bridge, and preparations were made for its reception. 



Thus a single dredging operation occupied a wJiole day. AVhen the dredge came 

 up the light was usually beginning to fail, and we were sometimes obliged to use 

 lanterns in clearing it. In hot cKmates it was unsafe to attem^Dt to keep creatures over 

 the night, they were almost sure to be half decomposed before morning ; they were 

 therefore registered and put into spirit at once, and we thus lost many opportunities of 

 observing in detail the colours of the animals, and the structure and consistence of their 

 fresh tissues. Animals from great depths were always brought up dead, so that we 

 had not to regret lost opportunities of watching their movements or habits. 



