GENERAL WALKER OFF AGAIN. – Among the passengers who left this port by the [Orizalis ?], was “Gen.” William Walker. During the month spent by him among us he has been exceedingly quiet, and has maintained his own counsel so well that no one has been able to obtain any positive indication of his business or purposes. That he came here to promote his long-cherished scheme of conquest in Nicaragua, we have good reason to believe; and the evidence is abundant that his agents are and have been for some time engaged in our midst in preparing to aid in another movement looking to that end; but nobody knows how far he has succeeded. We learn that he claims to have accomplished the purpose of his visit here, whatever it was, and that, although he took passage for the East via Panama, he contemplated the possible contingency of receiving news at Acapulco which would induce him to debark at that port. While he does not believe that either England or France would oppose him in Nicaragua by an issue of war, he [admits ?] that any new expedition there must be stronger, and better appointed, than either of the former ones; and distinctly intimates his expectation of leading such a one, at some time or other.