It does not materially alter the complexion of this question to say that propellers are generally constructed of iron. There is not such a difference in their prime cost or their stowage capacity as to enable them to take the large receipts necessary to their support; while certainly there is no advantage to be gained in speed from iron as a material of construction. The iron propeller can be constructed cheaper than the wooden in Great Britain, because of the great scarcity of timber and the large and redundant quantity of iron; and an iron vessel has some advantage in being able to stow a larger cargo, from the fact that her sides and bottom are not so thick as those of wooden vessels; but these considerations do not very materially affect the consumption of fuel, and the quantity necessary to carry a ton of freight. Iron is probably a better material than wood for the construction of propellers, as the part about the stern, where the screw works, can be made stronger, and as all iron vessels can be rather more readily divided into water-tight compartments by bulkheads. Yet as a material of construction it offers no transcendent advantages over the side-wheel for transatlantic navigation, while it is not probably so safe, or so comfortable for passengers. Yet, it will be well for us to adopt the propeller largely in our coasting trade, and iron as the material of its construction. We have thus seen that to save fuel and carry freight, the speed of the propeller must be low; indeed very low, if it is to live on its own receipts. It is therefore clearly impossible that with such comparatively low speed it should carry the mail. Neither can it support itself except by this low speed. By running thus but a fraction faster than the sailing vessel, it can command on a few prominent lines a large freight; but to give vessels of such speed a subsidy for carrying the mails would be both to render the mail service inefficient, and to enable the propeller to compete with the sailing lines of the country at very undue advantage, which would be an unfair discrimination against all sailing interests. Should the propeller, like the side-wheel, run fast enough on the average trips of the year to carry the mails, which would certainly be at the expense and abandonment of any considerable freighting business, then the Government might with propriety pay for the mails, as these steamers would not injure the freighting business of sailing vessels. The outcry by sail owners against steamers as competitors can not be against the mail packets; for these carry but little freight; but against these slow screws which should be treated like all other freighting vessels, notwithstanding the fact that some of their owners have had the impudence to propose them for the paid mail service and to ask a subsidy from the Government, but the better to cripple the interests of sailing vessels. As well might Government subsidize fast