ANOTHER GRAND SCHEME OF ANNEXATION. – We perceive from the proceedings of Congress yesterday, that Mr. Farnsworth (republican), of Illinois, asked leave to offer a long preamble setting forth the importance of our possessing all the British American provinces, concluding with a resolution instructing the Committee on Foreign Affairs to inquire into the expediency of initiating measures to secure them by honorable treaty. The resolution was objected to, perhaps as a slur at the Cuba thirty million proposition; but what objection can there be to the annexation of all British North America, if it can be bought? It would soon pay for itself from the public lands, fisheries, &c., which would thus be secured, and the Fugitive Slave law might thus be brought within reach of some thousands of runaway slaves on the other side of the Canadian boundary. With the Southern annexations of Cuba and Mexico, the North will doubtless insist upon the acquisition of the Canadas, New Brunswick, Nova Scotia, &c.; and what harm would there be in sounding the British government in advance? Let Mr. Farnsworth’s proposition have an airing. It is too grand to be treated as a joke.