But again, in a commercial point of view, I consider this the great question of the day. With the eastern front of our Republic stretching along the Atlantic and its western front along the Pacific, if all the parts should be united by a safe, easy, and rapid intercommunication we must necessarily command a very large proportion of the trade both of Europe and Asia. Our recent treaties with China and Japan will open these rich and populous Empires to our commerce; and the history of the world proves that the nation which has gained possession of the trade with eastern Asia has always become wealthy and powerful. The peculiar geographical position of California and our Pacific possessions invites American capital and enterprise into this fruitful field. To reap the rich harvest, however, it is an indispensable prerequisite that we shall first have a railroad to convey and circulate its products throughout every portion of the Union. Besides, such a railroad through our temperate latitude, which would not be impeded by the frosts and snows of winter nor by the tropical heats of summer, would attract to itself much of the travel and the trade of all nations passing between Europe and Asia. On the 21st of August last Lieutenant J. N. Maffit, of the United States brig Dolphin, captured the slaver Echo (formerly the Putnam, of New Orleans) near Kay Verde, on the coast of Cuba, with more than 300 African negroes on board. The prize, under the command of Lieutenant Bradford, of the United States Navy, arrived at Charleston on the 27th August, when the negroes, 306 in number, were delivered into the custody of the United States marshal for the district of South Carolina. They were first placed in Castle Pinckney, and afterwards in Fort Sumter, for safe-keeping, and were detained there until the 19th September, when the survivors, 271 in number, were delivered on board the United States steamer Niagara to be transported to the coast of Africa under the charge of the agent of the United States, pursuant to the provisions of the act of the 3d March, 1819, "in addition to the acts prohibiting the slave trade." Under the second section of this act the President is "authorized to make such regulations and arrangements as he may deem expedient for the safe-keeping, support, and removal beyond the limits of the United States of all such negroes, mulattoes, or persons of color" captured by vessels of the United States as may be delivered to the marshal of the district into which they are brought, "and to appoint a proper person or persons residing upon the coast of Africa as agent or agents for receiving the negroes, mulattoes, or persons of color delivered from on board vessels seized in the prosecution of the slave trade by commanders of United States armed vessels."