Having proceeded to the principal sorting carriage, we see that there are some thousands of the letters which have come from the London offices still to be disposed of. They lie on the desks in large bundles; but every minute there is a perceptible diminution of their numbers by means of the vigorous attacks of the men engaged. From end to end of one side of the carriage--that farthest from the platform--rows of sorting-boxes, or 'pigeon-holes,' are fixed nearly up to the roof, starting from the sorting-table, which is about three feet from the floor. The boxes into which the ordinary letters are sorted are divided into sets, numbered consecutively from 1 to 45, and one sorter works at each set. The numbers on the boxes are in accordance with a prescribed plan, each number representing the names of certain towns, and into such boxes the letters for those towns are sorted. The plan mentioned is carried out as follows: Suppose we say that No. 10 represents Rugby, of course when the mail-bag for that town is despatched the box is empty. It is then used, say, for Crewe, and when the bag for that place is gone the box again becomes empty. It is then used for some other town farther down the line, and so on to the end of the journey. The set of boxes nearest the fore-end of the carriage is used by the officer who deals with the registered letters. This set can be closed by means of a revolving shutter, which is fitted with a lock and key; so that, should the registered-letter officer have to quit his post for any purpose, he can secure the contents of his boxes, and so feel satisfied that they are in a safe place. This officer also disposes of all the letter-bills on which the addresses of the registered letters are advised. The set of boxes into which the newspapers and book packets are sorted is about twice the size of an ordinary letter set, and occupies the centre part of the whole box arrangement. This space is assigned to the newspaper boxes for two reasons: the set is exactly opposite the doorway through which the bags are taken in at the stopping station, so that they lie on the floor behind the sorter who opens them; he has therefore simply to turn round and pick them up one by one as he requires them, thereby saving both time and labour. Again, as the bags are opened, the bundles of letters which are labelled No. 1 and No. 2 respectively, in accordance with the list supplied to postmasters for their guidance, have to be distributed to the letter-sorters--No. 1 bundles to the left, No. 2 to the right; and this distribution could not be so conveniently performed with the newspaper or bag-opening table placed in a different position. Most of the newspaper boxes, as we have said, are about twice the size of a letter box; some, however, such as those used for large towns like Liverpool, Manchester, Birmingham, &c., are four times the size; and the necessity for this can be readily understood.