Rev. W. McLain, Washington.

Note.—This purchase makes the coast of Liberia 700 miles in length, along the whole course of which the Slave trade was formerly carried on to a great extent.

Extracts from the leading article in the African Repository and Colonial Journal for May, 1850, (the official organ of the Colonization Society,) on the establishment of the proposed line of Steamers.

The Colonization Society undertook to found a colony, to which the colored people might find it advantageous to emigrate. This has already been done. The work has been slow in its progress, as it were piling one stone upon other, till now the foundation is laid deep and wide. The Republic is sufficiently well established to receive a large number of emigrants yearly: there is room enough for them, and every thing invites them there, and these four steamers afford the facilities for their reaching there. It now only remains for the United States Government to adopt, foster, and encourage this work, and it will be done.

The great ends to be established present considerations of sufficient importance to induce the Government to comply with the prayer of the memorial. When these steamers are started the United States squadron on that coast may be withdrawn. It now costs upwards of $384,500 to maintain that squadron a year. These four steamers, and the emigrants carried out by them, will annually accomplish a thousand fold more for the suppression of the slave trade, than the squadron ever has or ever can accomplish! There cannot be a doubt of this. Does the United States Government desire the suppression of the slave trade? Undoubtedly. Here then is the way in which it may be done.

We may ask another question. Is it desirable that American commerce should be extended? Undoubtedly. Here then is a way in which it may be done. The 150,000,000 inhabitants of Africa, now all naked, must be clothed, and will be as civilization advances among them. They must have the means and appliances of agriculture and the mechanic arts. And in return for all these, they have all the rich and varied productions of tropical climates! How shall this work be accomplished? How shall Africa be civilized? How shall a market be opened there for all the articles manufactured in the United States, and for the surplus productions of our soil? How shall the inexhaustible treasures of that immense continent be brought to supply our wants, and increase our wealth and our glory?

By Colonization—by carrying out the plans and measures which the Society has adopted and been struggling to achieve. Already more than 80,000 of the natives have put themselves under the laws of Liberia, and are rising in the scale of humanity. Already there is a large demand for the productions of this country.

When the transported population of Liberia shall be 50,000 or 200,000, they will present a market for our surplus manufactures, and bread stuffs, of immense value. A line of settlements on the coast will command the commerce of the interior. If that power is held by men sent from this country by a large and liberal policy, nurtured and grown up under our institutions, and by our fostering care and aid, in establishing themselves in Liberia, they will ever be inclined to trade with this country, and thus open to our merchant, those wide fields of wealth! The amount asked by the Company from the Government for carrying the mails, would not affect injuriously one single interest of the country, and it would be more than repaid with interest by the advantages of the commerce to be secured thereby.

The advantages which would be enjoyed by the people of the United States as the result of the removal of the free colored people, and the separation of the races, would be immense. The blessings to them would be incalculable. They dwell among us, but they are not of us. They do not enjoy, and the prospect is, they never can enjoy here, true liberty! We provide for them a means of escape from these depressing circumstances, and place them in a situation were nothing can prevent them from rising to the highest elevation of which they are capable.