372 Mr. J. Y. Buchanan [May 29, 



The mean depth corresponding to 251 soundings with tempera- 

 tures, tabulated in the Eeport on ' Deep-sea Temperatures,' is 2060 

 fathoms, and 403 separate observations of the temperature at the 

 bottom were obtained. All the accidents, excepting two, happened 

 to the sounding line in the first sixty of these soundings, namely 

 before, and including, the 16th August, 1873. At the beginning 

 of the voyage only one thermometer was used at each sounding and 

 exactly sixty temperature observations correspond to these sixty 

 soundings. The breakages of the sounding line which occurred 

 during this period occasioned the loss of eleven thermometers, and 

 this was due principally to the use of the inferior sounding line 

 (No. 2) during the first months of the voyage. 



At almost every one of the remaining soundings, 191 in number, 

 two thermometers were used. The exact number of individual obser- 

 vations of temperature at the bottom was 343. We have seen that 

 during this time, from August 1873 to the end of the voyage in 

 May 1876, only two sounding lines were carried away, namely, those 

 of the 14th and 16th June, 1874, entailing a loss of four thermometers. 

 Therefore, in two years and nine months, 343 independent observa- 

 tions of the temperature at the bottom, in an average depth of 2060 

 fathoms, were made at an expenditure of four thermometers. This is 

 at the rate of, in round numbers, 86 determinations per thermometer 

 lost. After leaving New Zealand, the whole of the exploration of 

 the Pacific Ocean, occupying eighteen months, was carried out without 

 the loss of a sounding line or of a thermometer, or other instrument 

 attached to it. One thermometer was lost by the parting of the tem- 

 perature line on June 18, 1875. It may be added that, during the 

 whole voyage, eleven thermometers collapsed under the high pressure, 

 at very great depths. 



We see then that, at a full station of average depth the length of 

 sounding line handled was — 



For the sounding ...... 2060 fathoms 



For intermediate temperatures .... 2500 „ 



And for intermediate waters .... 1875 „ 



Total . .6435 



When the depth was 3000 fathoms or more the length of sounding 

 line handled in the day amounted to from 7500 to 8000 fathoms. 

 In addition to this there would be the 3000 fathoms of dredge-line. 



In dredging and trawling the Challenger was equally successful. 

 From the date of sailing from England to October 3, 1873, or nine 

 months, the dredge or trawl line parted six times. From October 3, 

 1873, till June 26, 1875, 113 stations, no line parted. In 1875 three 

 lines, and in 1876, two lines parted. In all during three- aud-a-half 

 years, during which 354 stations were made, there were only eleven 

 cases of the parting of the dredge or trawl line. 



In the ordinary routine on board the Challenger the sounding 



