As much has been said of Propellers during the few years past, I propose examining the question with the view of ascertaining whether they are adapted to the mail service, and whether we can secure from them sufficient speed without a subsidy from the Government. It is well known that the British are a far more steady-going people than ourselves, and not being so rushing do not require so much speed. They have had an easy control of the European and foreign commerce generally around them; and when competition aroused them to additional efforts they did not endeavor to outstride themselves, but took merely an additional step of progress and speed, and adopted the propeller for their coasting business, because it was a little faster than wind, and yet cheaper than full steam. And because so many propellers have been built for the peculiar short-route trade of Great Britain, many people in this country can not see why we do not adopt the propeller for our foreign trade. I have already shown (_See page 44_) that there are some short routes on which steam is cheaper than the wind, and that on others of greater length steamers can not transport freight under any conditions. (_See latter part of Section IV., on the Cost of Steam._) I do not propose making the Screw Propeller in any way an exception to the position stated; and shall consequently maintain that it will never be the means of attaining a rapid and yet cheap mail speed. There are no greater errors entertained by the public on any subject connected with steam navigation than concerning the Screw Propeller. It is generally supposed that it is a more economical and effective application of power than the side-wheel, which is a mistake: it is generally supposed that, with the same amount of power and all other conditions equal, the propeller will not run as rapidly as the side-wheel, which is true of steaming in a sea-way or against a head-wind, but a mistake as regards smooth water: it is generally supposed that the engines weigh less, take up less room, and cost less, which is all a mistake. The best authors on this subject and the most eminent builders generally agree, that in England and Scotland, where the propeller has attained its greatest perfection, the difference between the side-wheel and the propeller as an application of power is very slight and hardly appreciable; or that the same number of tons of coal will drive two ships of the same size at the same speed in smooth water; but that the side-wheel has greatly the advantage in a head-sea or during rough weather generally. Many persons who do not understand the subject, have theorized in just the contrary direction. They say that in rough weather the screw has the advantage, because it is alway in the water, etc. Experience shows just the reverse; and theory will bear the practice out. If, in the side-wheel one wheel is part of the time out, the other has, at any