vi PREFACE. 
library on board the Challenger, excellent under the circum- 
stances, it was of course by no means complete enough to en- 
able us to go with safety into matters of detail. Still, notwith- 
standing these difficulties, it seemed to me so desirable that a 
sketch of our proceedings and of the more important results 
of the Expedition should be made public at as early a date as 
possible, that I determined to make the attempt. 
At first I hoped that it might have been possible to make 
the publication of the journal almost keep pace with the voy- 
age, or that, at all events, the rough results of one year’s work 
might have been published during the next; and accordingly 
a great part of the first volume was written and put into type 
during the year 1874. I found, however, that this was imprac- 
ticable. The uncertainty of communication became greater as 
the voyage proceeded; and inevitable delays having occurred, 
further observations constantly made it necessary to modify 
previously formed opinions, or desirable to strengthen them by 
additional evidence. 
We arrived in England on the 24th of May, 1876, with the 
rough journal of the cruise in a sense complete, but not in a 
form for publication. From the amount of work thrown upon 
my hands in getting the collections into order, and having ar- 
rangements made for the working-out of the scientific results, 
the difficulties in the way were even greater than they had been 
on shipboard ; and now, nearly a year after our return, the first 
two volumes only are completed. 
In a former volume* I have given a general history of deep- 
sea investigations. I have described with some minuteness 
the appliances and methods employed during the preliminary 
cruises of the Lightning and Porcupime in ascertaining the 
* “The Depths of the Sea.” Second Edition. Macmillan & Co. 
