He had said nothing yet to Mr.Gibbs in regard to the matter.

Every day he made a report to Roland Clewe about Rovinski, but Clewe's instructions were that so long as the Pole behaved himself properly there was no reason to trouble the minds of the party on board with fears of rascality on his part.

They had enough to occupy their minds without any disturbing influence of that sort.
Clewe's own opinion on the subject was that Rovinski could do nothing but act as a spy, and afterwards make dishonest use of the knowledge he should acquire; but the man had put himself into Clewe's power, and he could not possibly get away from him until he should return to Cape Tariff, and even there it would be difficult.

The proper and only thing to do was to keep him in custody as long as possible.

When he should be brought back to a region of law and justice, it might be that the Pole could be prevented, for a time, at least, from using the results of his knavish observations.
There was another person on board whose mind was disturbed by Rovinski.
This was Mr.Marcy, the Assistant Engineer, an active, energetic fellow, filled with ambition and love of adventure, and one of the most hopeful and cheerful persons on board.