Answer:
"The correspondent thought that he was the one man afloat on all the oceans."
Explanation:Mood is illustrated as the atmosphere or setting that envelops a literary work created by the use of varied words and descriptions by the author with an intention to elicit desired emotions or feelings.
In the given excerpt, the detail that best conveys a mood of 'loneliness' would be 'The correspondent thought that he was the one man afloat on all the oceans'. 'One man' here implies the isolated atmosphere which is comprehended by the use of words like 'fragmentary', 'dull', 'sadder', etc. These descriptions together contribute to elevate the central idea of desolation and solitude in the excerpt.