PREFACE. 
Tursr two volumes consist chiefly of an abstract of the less 
technical portions of my own journal for the first year of the 
voyage of the Challenger (1873), and the early part of the 
fourth year (1876), when she again traversed the Atlantic on 
her way home. With these I have incorporated some of the 
more novel results of the observations of my colleagues, and I 
have added, usually in the form of Appendices, such Meteoro- 
logical Tables, Tables of Depths and of Sea-temperatures, and 
Tables of Specific-gravity Determinations, as shall be sufficient 
to place in the hands of our fellow-workers in the field of Phys- 
ical Geography, at all events, an abstract of the data on which 
our conclusions and speculations are founded, and enable them 
to judge for themselves. 
I had much hesitation in attempting to prepare these vol- 
umes for publication at sea. For the last four years the duties 
of each day have nearly fully oceupied our time: our minds 
have been continually distracted by new impressions and by 
the necessity of devoting undivided attention to new objects 
of interest. Ship-life is generally unfavorable to steady work; 
and during a great part of the time the motion of the ship 
makes it impossible to have even the limited space at one’s 
command in his cabin, littered with papers and journals and 
memoranda in the orderly confusion which is inseparable from 
comfortable literary work. Although there was a reference 
