While this is true, there is no work on this general subject to which persons can refer for the authoritative settlement of any of these points, either absolutely or proximately; and while a simple statement of facts, acknowledged by all steamship-men, may tend to dispel much misapprehension on this interesting subject, it will also be not unprofitable, I trust, to review some of the prominent arguments on which the mail steamship system is based. That system should stand or fall on its own merits or demerits alone; and to be permanent, it must be based on the necessities of the community, and find its support in the common confidence of all classes. I have long considered a wise, liberal, and extended steam mail system vitally essential to the commerce of the country, and to the continued prosperity and power of the American Union. Yet, I am thoroughly satisfied that this very desirable object can never be attained by private enterprise, or otherwise than through the direct pecuniary agency and support of the General Government. The abandonment of our ocean steam mail system is impossible so long as we are an active, enterprising, and commercial people. And so far from the service becoming self-supporting, it is probable that it will never be materially less expensive than at the present time. It has been my constant endeavor to give the best class of authorities on all the points of engineering which I have introduced, as that regarding the cost of steam and high mail speed; and to this end I have recently visited England and France, and endeavored to ascertain the practice in those countries, especially in Great Britain. I desire to return my sincere acknowledgments for many courtesies received from Mr. Charles Atherton, of London, England; Robert Murray, Esq., Southampton; and Hon. Horatio King, of Washington, D. C. THOMAS RAINEY. New-York, _December 9, 1857_. THE ARGUMENT. 1. _Assumed_ (Section I.) _that steam mails upon the ocean control the commerce and diplomacy of the world; that they are essential to our commercial and producing country; that we have not established the ocean mail facilities commensurate with our national ability and the demands of our commerce; and that we to-day are largely dependent on, and tributary to our greatest commercial rival, Great Britain, for the postal facilities, which should be purely national, American, and under our own exclusive control:_ 2. _Assumed_ (Section II.) _that fast ocean mails are exceedingly desirable for our commerce, our defenses, our diplomacy, the management of our squadrons, our national standing, and that they are demanded by our people at large:_