226 CHALLENGER 



from a large reel fitted in one of the ship's boats. The line was 

 marked every loo fathoms and while the line ran out the time 

 was noted as each mark left the reel. When the time interval 

 between two marks appreciably lengthened the weight at the 

 line's end was assumed to have reached the bottom and the 

 amount of line out taken to indicate the depth. 



The procedure in the boat was necessarily one for calm weather 

 and this restricted the number of successful casts made in the 

 open sea; with this apparatus, however, the first 'abysmal' sound- 

 ings, as the oceanographic text-books call them, were taken and 

 2425- fathoms was plumbed in the South Atlantic in 1840. 



One of the early snags of deep sounding was that a heavy weight 

 was needed to take the line down, but to recover such a weight 

 with the bottom sample adhering to it a very bulky line was 

 required. There was in the United States Navy at this time the 

 now famous officer, Lieutenant Maury, who had produced num- 

 erous wind and current charts and sailing directions for mariners. 

 Working under him was a Midshipman Brooke, who about the 

 year 1 8 g^ constructed an apparatus which took a sample of the 

 sea-bed and then detached the bulk of the heavy weight which 

 had taken it down, leaving only a light tube, inside which the 

 sample was retained, to be hauled back to the surface. This in- 

 vention speeded up the sounding of the oceans and in 18^4 

 Maury was able to make the first bathymetric chart of the North 

 Atlantic. This apparatus, modified by Lieutenant Baillie, Royal 

 Navy, and named after him, is still in use today. 



The earlier Challenger Expedition is said to have carried wire 

 for sounding purposes, but for some reason this was not used and 

 the method of using marked rope and time intervals was em- 

 ployed for taking the many ocean soundings which this vessel 

 made. Her deepest for the voyage was 45^00 fathoms, recorded 

 in the Marianas Trench where the recent Challenger found her 

 deepest sounding referred to above. 



The U.S.S. Tuscarora was also at sea employed upon oceano- 

 graphic work at the time of the Challenger Expedition and it 

 was from her that piano wire was first used for sounding great 

 depths. With this wire she sounded 465^5- fathoms just east of the 

 Kuril Islands in the northern part of the Japan Trench, 



The first ship to sound at a greater depth than ^000 fathoms 



