2. The knowledge of the following misconception may also help to save the public and the Post-Office a great amount of trouble. "It is often assumed," says the Postmaster-General, "that a mail-conveyance passing by, or through a place, ought, as a matter of course, to deposit," there and then, "the letters directed thereto; the practice being, on the contrary, that until the mail arrives at the head post-office of the district, the letters in question are not separated from the other letters of the district. A slight consideration of the nature and objects of the postal service will show that such separation cannot be effected in any other way, unless, indeed, the mail-conveyance, even supposing it to be but a _mail-cart_, were converted into a travelling post-office, and furnished with clerks of unlimited local knowledge (which is plainly impossible), or unless every town and village in the kingdom, having any correspondence with the place in question, were to make up a bag for that place; in which case its mail would contain nearly as many bags as letters." 3. "It happens from time to time that, owing to the stream of postal communications having been diverted from the old mail-road to a line of railway, or from other causes of like nature, it becomes desirable to reduce the post-office of a town from the condition of a _principal_ office to that of a _sub_-office. This step not unfrequently gives rise to complaints, the inhabitants being under the impression that they will not in future be so well served. This is a misconception. The change is not made when it will subject the correspondence to delay; nor does it cause any withdrawal of accommodation in respect to money-orders. It is, in fact, only a departmental arrangement, which consists in carrying on the sorting of the letters for the new sub-office at some intermediate office, instead of sending the letters in direct bags."