was always of the same opinion, and has declared it a hundred times. In his Marshfield speech, September 1, 1848, he said, “He [General Cass] will surely have the Senate, and with the patronage of the government, with every interest that he, as a northern man, can bring to bear, coöperating with every interest that the south can bring to bear, we cry safety before we are out of the woods, _if we feel that there is no danger_ [of slavery] _as to these new territories_.” Up to the 7th of March, 1850, then, when he abandoned all the doctrines and sentiments he had ever before advocated on this subject, and when he incurred the public, hearty approval and encomiums of Mr. Calhoun, by his moral agility in springing, at one leap, from Massachusetts to South Carolina;--until this time, Mr. Webster had always held, that slavery would invade the new territories if not barred out of them by positive law. And what would be still more remarkable, if the doctrines of the 7th of March speech had the least shadow of soundness in them, is, that they have now been before the public for more than four months, and, so far as I know, not a single southern man has been converted by them. Are not Mr. Benton, Mr. Mason, Colonel Davis, and thousands of others, individually, as good judges, or as good witnesses, as he is? Since the speech, the people of New Mexico have prohibited slavery in their constitution, because they knew it to be possible among them. Before the speech, California did the same, and for the same reason. The Nashville convention has just resolved, “That California is peculiarly adapted for slave labor, and that if the tenure of slave property was by recognition of this kind secured in that part of the country south of 36° 30´, it would in a short time form one or more slaveholding states, to swell the number and power of those already in existence.” Even those who seek to apologize for Mr. Webster, avow, at the same time, their disbelief in his doctrine. Such is the evidence, on the one side and on the other, as to the possibility or impossibility of slavery in the territories. Mr. Webster is against the whole world, and the whole world is against him, and this, too, on a question already settled by history and experience. He is just as much to be believed, as a man who looks up into the clear midnight sky, and denies the existence of the heavenly host, while all the stars of the firmament are shining down into his eyes. To increase the overwhelming proof against Mr. Webster, I add the following:-- HOUSE OF REPRESENTATIVES, June 1, 1850. HON. S. R. THURSTON, Delegate from Oregon.