If possible, not to let the men so much as surmise that their officers anticipate aught amiss from them is the tacit rule in a military ship. And the more that some sort of trouble should really be apprehended the more do the officers keep that apprehension to themselves; tho' not the less unostentatious vigilance may be augmented.
In the present instance the sentry placed over the prisoner had strict orders to let no one have communication with him but the Chaplain. And certain unobtrusive measures were taken absolutely to insure this point.

What It Means

This is a placeholder explanation generated by the low-overhead model. It interprets "If possible, not to let the men so much as surmise that their officers anticipate aught amiss from them is the tacit rule in a military ship. And the more that some sort of trouble should really be apprehended the more do the officers keep that apprehension to themselves; tho' not the less unostentatious vigilance may be augmented.
In the present instance the sentry placed over the prisoner had strict orders to let no one have communication with him but the Chaplain. And certain unobtrusive measures were taken absolutely to insure this point." in the context of "Ch. 23" to mean that wisdom is timeless.