Mr. Sumner occupied several weeks of this summer in a tour to the West, ascending the Mississippi to St. Paul, and then, from Detroit, visiting Lake Superior. While on board a steamer in Lake Superior, he learned by the newspapers that Passmore Williamson, an excellent citizen of Philadelphia, had been flung into prison for the offence of reminding a person claimed as slave, that, being brought to Philadelphia voluntarily by her pretended master, she was free, according to well-known principles of jurisprudence. The indignation of Mr. Sumner found expression in the following letter, which he addressed to the new victim of Slavery. This remarkable case will be found in a volume published at Philadelphia, in 1856, with the following title: “Case of Passmore Williamson. Report of the Proceedings on the Writ of Habeas Corpus issued by the Hon. John K. Kane, Judge of the District Court of the United States for the Eastern District of Pennsylvania, in the Case of the United States of America _ex rel._ John H. Wheeler _vs._ Passmore Williamson, including the several Opinions delivered, and the Arguments of Counsel, reported by Arthur Cannon, Esq., Phonographer.” From this it appears that John H. Wheeler, of Virginia, in a petition to Hon. John K. Kane, Judge of the District Court of the United States for the Eastern District of Pennsylvania, dated July 18, 1855, sets forth, that he is “the owner of three persons held to service or labor by the laws of the State of Virginia, said persons being respectively named Jane, aged about thirty-five years, Daniel, aged about twelve years, and Isaiah, aged about seven years, persons of color, and that they are detained from the possession of your petitioner by one Passmore Williamson, resident of the city of Philadelphia, and that they are not detained for any criminal or supposed criminal matter,” and asks a writ of _Habeas Corpus_ commanding Mr. Williamson to bring before the Judge the bodies of the said Jane, Daniel, and Isaiah. The writ was at once allowed, and the next day followed by another, to which Mr. Williamson made return, that “the within named Jane, Daniel, and Isaiah, or by whatsoever names they may be called, nor either of them, are not now, nor was at the time of the issuing of said writ or the original writ, or at any other time, in the custody, power, or possession of, nor confined nor restrained their liberty by him, the said Passmore Williamson. Therefore he cannot have the bodies of the said Jane, Daniel, and Isaiah, or either of them, before your Honor, as by the said writ he is commanded.” In the course of the proceedings, Mr. Williamson, who was Secretary to the Acting Committee of the Pennsylvania Abolition Society, testified as follows.