1903.] on Some Problems and Methods of Oceanic Besearch. 369 



was first used in America by Agassiz in 1877, and on this side of 

 the Atlantic by myself in 1878. 



Wire is suitable only for sounding, pure and simple ; and the 

 detailed investigation of the form of the bottom of the ocean cannot 

 be carried out with anything else. As there is nothing at the end 

 of the wire but a sounding tube or a sinker, it can be hove up as 

 quickly as the engine will run, and the loss owing to a breakage of the 

 wire is insignificant. For deep-sea research it is entirely unsuitable, 

 because it has to carry valuable instruments. Their value increases 

 largely with the number of times that they are employed, and when 

 they are lost, for instance, in the Pacific, it takes the best part of a 

 year to replace them, and then they are replaced by new instruments 

 which have no history. 



The record of the Challenger in freedom from accidents is a very 

 brilliant one. She was supplied with two qualities of sounding line 

 designated Nos. 1 and 2, of which No. 2 was inferior in size and 

 quality. It was used during the first two months of the cruise and 

 was found so untrustworthy that it was condemned, and from Feb- 

 ruary 1873 line No. 1 was used exclusively. Before reaching Lisbon 

 three No. 2 lines were lost, with three thermometers. After leaving 

 Lisbon the No, 2 line was used for the last time on February 19, 1873, 

 when it parted, and two thermometers were lost. From this date 

 until the end of the voyage in May 1876, No. 1 line was used ex- 

 clusively, and it parted on five occasions, namely, April 28, 1873, 

 losing one thermometer ; on May 1, 1873, losing one thermometer ; 

 on August 16, 1873, losing two thermometers; and on June 14: and 

 June 16, 1874, losing on each of these days two thermometers. After 

 June 16, 1874, no sounding line was lost. In all, therefore, nine 

 sounding lines were lost, and along with them thirteen thermometers. 

 During the whole voyage only two temperature lines were lost with 

 eight thermometers. This immunity from accident was due not only 

 to the excellence of the line, but in a far greater degree to the con- 

 stant care which was taken of it by the ofiicers and men who had 

 charge of it. 



The immunity from breakage of the sounding line enabled the 

 temperature at the bottom of the ocean to be determined time after 

 time with the same thermometer, and even with the same pair of 

 thermometers. The following is a list of the thermometers which were 

 used more than ten times for determining the bottom temperature. 



Thermometer . . No. 93 69 68 87 86 83 92 66 89 

 Times used .... 78 74 31 29 23 15 13 20 11 



In the following table will be found the number of times that 

 certain pairs of thermometers were used together for the determi- 

 nation of the bottom temperature at the same locality. 



69 69 

 83 66 

 Times used together ... 28 13 12 



Thermometers .... Nos. |gg go qq 



