We now come to still later issues--to the discussion between Mr. Douglas and his southern enemies, in the last session of the thirty-fifth Congress--the present year--upon Congressional intervention in favor of slavery. This great debate took place Feb. 23, 1859, in the Senate, and looked like a preconcerted attack upon Mr. Douglas by some of his southern opponents. We have not the space for the official report of the debate, and will endeavor faithfully to abridge it. The debate opened on an amendment by Senator Hale to the Appropriation bill before the Senate to repeal the restrictive clause of the Kansas Admission act. This amendment was offered the day previous, and the debate took an unexpected turn upon it. Mr. Seward, of New York, said Congress had decided that Kansas should come in with the Lecompton Constitution, without reference to population; but, on the other hand, should not come in outside of the Lecompton Constitution unless she had 92,400 population. There was, therefore, a discrimination by the Congress of the United States, as against freedom, in favor of slavery. Oregon, because she was a Democratic State, was admitted without reference to population, and Kansas, because of her different politics, was excluded. He was glad of this occasion to renew his vote. He was glad, also, to hear that so many gentlemen on the other side will give Kansas a fair hearing. It indicates that the time is coming when any State applying for admission will be heard on its merits, apart from all other considerations. He thought it goes to show that if Texas should be divided, or free States, as he thought they would, be formed in Mexico, they will come in as free States. Mr. Brown, of Mississippi, made a strong southern speech. He held to the doctrine of State rights; denied the squatter sovereignty of territories; and threatened secession, with banners flying, if the South was deprived of her rights. His address was directed to northern Democrats. He placed his views frankly on record, and desired neither to cheat nor be cheated.