But although none of these powers, in their present state, be so perfectly adapted to the propulsion of the Balloon as to leave nothing further to desire, yet are some of them so far applicable as, undoubtedly, to enable us to accomplish, by their means, a very large amount of success. A steam engine of the power required, namely, equal to fourteen horses, could be easily constructed, far within the limits of weight which we have at our disposal upon that account in the Balloon under consideration, or even in one much smaller; and recent improvements have so far reduced the amount of coal required for its maintenance, that perhaps as long a voyage could be made by means of it now, as would be expected or required. Even human strength, by a certain mode of applying it, might be made effectual to the accomplishment of a very sufficient rate of motion, say fourteen or fifteen miles an hour, for, continuously, as long a period as the natural strength of man, moderately taxed, could endure, and which we may reckon at twelve hours. It is true that neither the velocity here quoted, nor that before assumed is so great as to enable the aeronaut to compete with some of the modes of transit employed on the surface of the earth; as, for instance, the railroads, where 25 miles an hour is not an unusual speed. Yet is not the aerial machine which could command such a rate of motion to be despised, or set aside as inferior in actual accomplishments to what is already at our disposal; for it must not be lost sight of, that railroads, or terrestrial roads of every description, must ever be limited in their extent and direction, and travelling on them, however perfectly contrived, subject to deviations and interruptions, particularly in passing from one country to another beyond the seas, which if taken into account, would reduce the apparent estimate of their rates, considerably under the lowest of those assigned to the Balloon in the previous calculation; and at all events, by sea, much less, under the most favourable circumstances is the ordinary rate of ships.