Latest News.—The lowa [steam boat] passed down (6 o'clock Wednesday evening) and reports that she was not allowed to land her passengers at Nauvoo the city having been declared by the prophet, under Martial Law.

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Thursday, June 20, 7 o'clock P.M.

We stop the press for the purpose of presenting our readers with additional proof of the declaration of Martial Law, in Nauvoo. Two gentlemen left this place on the 18th inst. for that city. They arrived during a severe shower of rain, and were not molested until they had reached the Mansion House. They were then told that they could not leave the city without a pass! The same was reiterated by Joe Smith, with the additional remark, that all who were there should be made to remain and fight for him.— Sentries were stationed throughout the city, and as far as they could judge, the most rigid adherence to Military Law was observed. One of the gentlemen, was so fortunate as to have an acquaintance in the city, through whose urgent solicitation, backed by assurances of good intentions, they were enabled to procure a pass.

While in the city, they were closely questioned, as to their residence, business and destination, by persons who appeared to act by authority.

They also report that several persons are in the city under arrest. One family of emmigrants, bound for Iowa were detained, being unable to procure a pass.