In the circulation of letters, we may discover the paradox that "the longest road is often the shortest"; the explanation of which is, that by a round-about way letters may sometimes arrive sooner than by waiting the next chance by a more direct route. Post-office circulation is not tied down by any strait-laced lines of geographical science, nor by any consideration but that of the economy of time. For example, at certain periods letters from Edinburgh for places in Norfolk and Suffolk go on to London, to return north to those counties by the mails out of London; similarly, letters for places north of Manchester are at certain hours sent on to that city, to be returned part of the way by next opportunity. It will no doubt seem a puzzle that letters for Ireland should, at a certain time of day, be forwarded from Edinburgh to Leeds in Yorkshire! Yet this is so, and with good results,--the fact being that, after the more direct despatches for the day, Irish letters are sent by the last evening train to Leeds, whence early next morning they are sent across the country, reaching a travelling post-office proceeding from London to Holyhead, and then catching the day-mail packet for Ireland. Thus they arrive in the sister isle by the time they would otherwise be only leaving Scotland. In the travelling post-offices the plan of carrying letters away from their destinations in order that time may be gained for their sortation, and afterwards sending them back by a Post-office carriage proceeding in the reverse direction, is largely practised, and with the greatest advantage. Again, letters from Newcastle-on-Tyne for Glasgow, forwarded by the night-mail, take what might be thought to be a very wide circuit--namely, by way of Normanton in Yorkshire, and Manchester and Wigan in Lancashire; yet that circulation is found to be best at the hour at which the night-mail despatch is made. In one more case that may be cited, letters from Berwick-on-Tweed for Carlisle are, at a certain time of the day, forwarded through Edinburgh as the most expeditious route. There is such a complexity of arrangement in the matter of circulation, and so great a dependence of any one part on a great many other surrounding parts, that comparatively few persons ever thoroughly understand it, and only those who can master it should meddle with it.