In the autumn of 1845, Mr. Wilson declined being a candidate for the Senate, and was chosen Representative from the town of Natick. In the legislature he introduced a resolution announcing the unalterable hostility of Massachusetts to the further extension and longer existence of slavery in America, and her fixed determination to use all constitutional and legal means for its extinction. In spite of the coldness and opposition of several leading Whigs, this resolution was adopted by ninety-three majority in the House, but was lost in the Senate by four votes. Mr. Wilson made an elaborate speech in its behalf, and Mr. Garrison, in the "Liberator," pronounced it the fullest and most comprehensive speech upon the slavery question, ever made in any legislative body in this country. In 1846, Mr. Wilson declined to be again a candidate for the legislature. In 1843, the officers of the First Regiment of Artillery elected Mr. Wilson its Major without his knowledge. He accepted the position, and in June, 1846, he was chosen Colonel, and was elected Brigadier General of the Third Brigade in August, which position he continued to hold for five years. In March, 1848, a Whig district convention was held at Dedham, to nominate a candidate for Congress to fill the vacancy occasioned by the death of John Quincy Adams. Henry Wilson, Horace Mann, and William Jackson, were the leading candidates. After three ballotings Mr. Wilson declined being considered a candidate, and Mr. Mann was nominated. The convention, at the same time, by an almost unanimous vote, elected Mr. Wilson a delegate to the National Whig Convention. That the vote was not unanimous was owing to the fact that he had stated in public and in private that if General Taylor should be fixed upon by the Whig party as its candidate, unpledged to the Wilmot Proviso, he not only would not support him, but would do all in his power to defeat him. When General Taylor was nominated, and the Wilmot Proviso voted down by the Whig National Convention, in June, 1848, General Wilson, and his colleague, Hon. Charles Allen, denounced the action of the convention, and left it. Gen. Wilson then got up a meeting of a few northern men, which was held in the evening, to consider what steps should be taken. Gen. Wilson called the meeting to order, and after stating its purposes, moved the appointment of a committee to call a convention of the opponents of the Slave Power. The committee was accordingly appointed, and united with others in calling the Buffalo Convention, which nominated Mr. Van Buren and Mr. Chas. Francis Adams.