by two wheels rolling upon this wire; the cases being so constructed as to enable the wheels to pass unimpeded by the fixed supports of the wire.  An endless wire of much smaller size must pass over two drums, one at each end of the station.  This wire should be supported on rollers, fixed to the supports of the great wire, and at a short distance below it.  There would thus be two branches of the smaller wire always accompanying the larger one; and the attendant at either station, by turning the drum, might cause them to move with great velocity in opposite directions.  In order to convey the cylinder which contains the letters, it would only be necessary to attach it by a string, or by a catch, to either of the branches of the endless wire.  Thus it would be conveyed speedily to the next station, where it would be removed by the attendant to the commencement of the next wire, and so forwarded.  It is unnecessary to enter into the details which this, or any similar plan, would require.  The difficulties are obvious; but if:  these could be overcome, it would present many advantages besides velocity; for if an attendant resided at each station, the additional expense of having two or three deliveries of letters every day, and even of sending expresses at any moment, would be comparatively trifling; nor is it impossible that the stretched wire might itself be available for a species of telegraphic communication yet more rapid.

Perhaps if the steeples of churches, properly selected, were made use of, connecting them by a few intermediate stations with some great central building, as, for instance, with the top of St Paul’s; and if a similar apparatus were placed on the top of each steeple, with a man to work it during the day, it might be possible to diminish the expense of the two-penny post, and make deliveries every half hour over the greater part of the metropolis.

337.  The power of steam, however, bids fair almost to rival the velocity of these contrivances; and the fitness of its application to the purposes of conveyance, particularly where great rapidity is required, begins now to be generally admitted.  The following extract from the Report of the Committee of the House of Commons on steamcarriages, explains clearly its various advantages: 

Perhaps one of the principal advantages resulting from the use of steam, will be, that it may be employed as cheaply at a quick as at a slow rate; ’this is one of the advantages over horse labour. which becomes more and more expensive as the speed is increased.  There is every reason to expect, that in the end the rate of travelling by steam will be much quicker than the utmost speed of travelling by horses; in short, the safety to travellers will become the limit to speed.’  In horse-draught the opposite result takes place; ’in all cases horses lose power of draught in a much greater proportion than they gain speed, and hence the work they do becomes more expensive as they go quicker.’