|Havana, | | Savannah Steamship Co., |New-York and Savannah, | 4| 4,793 New-York and Charleston St. S.| " " Charleston, | 4| 4,680 Co.,| | | " " Virginia, | " Norfolk, and Richmond, | 2| 2,371 Philadelphia and Savannah, |Philadelphia and Savannah, | 2| 2,600 Boston and Baltimore, |Boston and Baltimore, | 2| 1,600 Texas Steamship Co., |New-Orleans and Galveston, | 4| 2,400 Southern Steamship Co., | " " Key West, | 2| 1,000 Mexican Steamship Co., | " Tampico and Vera Cruz,| 1| 960 ------------------------------+--------------------------------+------+-------- [K] Building another steamer of 2,500 tons for the Brazil line. [L] These vessels average about 250 horses' power each. Their tonnage is large, probably 1,200 tons each. There are several other lines of ocean steamers in Europe; but it is almost impossible to ascertain anything definite about them. The list above embraces all of the most important companies of the world. The lines are continually changing, while the vessels are passing into new hands almost every week. PAPER G. The following official letter from Hon. Horatio King explains itself. Post-Office Department, } Washington, Nov. 12, 1857. } Sir: In answer to your letter of 10th inst., I have to inform you, that the ocean mail steamship lines now under contract with the Government for the conveyance of mails, are as follows, namely: 1. The New-York and Liverpool (Collins) Line, performing twenty round trips per annum, at an annual compensation of $385,000. Length of route, 3,100 miles. 2. The New-York and Bremen Line, _via_ Southampton, performing thirteen round trips per annum, for the gross amount of United States postages, (sea and inland.) Length of route, 3,700 miles. 3. The New-York and Havre Line, _via_ Southampton, performing thirteen round trips per annum for the gross amount of United States postages, (sea and inland.) Length of route, 3,270 miles. 4. The New-York, Havana, New-Orleans, and Aspinwall Line, performing twenty-four round trips per annum, at an annual compensation of $290,000. Length of routes 2,000 miles from New-York to Aspinwall _direct_; 2,000 miles from New-York to New-Orleans _via_ Havana; and 1,200 miles from Havana to Aspinwall; making in all, 5,200 miles. 5. The Astoria, San Francisco, and Panama Line, performing twenty-four round trips per annum, at an annual compensation of $348,250. Length of route, 4,200 miles.