Vlll THE V^OYAGE OF H.M.S. CHALLENGER. 



and the discussion of the correlation and the general bearings of the results in 

 all the departments.' This part has been relegated in the present instance 

 to a staff of specialists under my direction. 



The preparation of the Hydrographical and Physical Report would natu- 

 rally have devolved upon Sir George S. Nares, K.C.B,, F.R.S., under whose 

 direction the whole system of observation was carried out during the first 

 two years of the voyage. When Captain Nares was recalled to take com- 

 mand of the Arctic Expedition which left England in 1875, he was succeeded 

 in the command of the Challenger by Captain Thomson, and by the wish 

 of that officer the same system was continued during the remainder of the 

 cruise, the Hydrography and Meteorology being under the superintendence 

 of Staff-Commander Tizard, in whose hands Captain Nares most liberally 

 left his notes and memoranda. When the ship returned to England in 1876, 

 the Hydrographer of the Admiralty, who has throughout taken the warmest 

 interest in the success of the undertaking, so adjusted the duties of Staff- 

 Commander Tizard that that officer has been able to give his effective 

 assistance in the preparation of the Report. All the charts and plans have 

 been prepared under his superintendence ; and all the physical data which 

 occur, whether in the first volume, to which his name is attached, or in the 

 volumes- devoted to special subjects, have been supplied or revised by him. 



For the general instructions under which the expedition was despatched, 

 I must refer to Appendix A of the first volume of the Report. I need only 

 mention here that one of our principal objects of inquiry was the nature and 

 distribution of the fauna of the ocean basins, and the form under which life 

 was maintained under different physical conditions ; and that my own instruc- 

 tions as to the conduct of the zoological investigations were very general, the 

 details being left almost entirely to my own discretion. Three gentlemen 

 versed in different branches of Zoology were associated with me in this 



