Envelopes. Until the introduction of the penny-postage system, envelopes for written letters were very little adopted; it was far more customary to secure by wafer or sealing-wax the folded sheet of paper on which the letter was written. When the postage was rendered uniform for all distances, and prepayment enforced, or at least recommended, it was supposed that stamped envelopes would be convenient coverings for letters, sealing the letter and paying the postage at one operation. These, however, were soon found to be inconvenient, and the great development of envelope manufacture has taken place in the direction of unstamped varieties of envelopes, to which, of course, adhesive stamps can be attached. During the last half-century this development has taken place to an extent that no one could have contemplated. Several large firms in England and Scotland, as well as abroad, are engaged in it, and the quantity of envelopes turned out is simply enormous; the largest producers being Messrs Pirie of Aberdeen, whose turn-out amounts to upwards of thirteen millions per week.
In the manufacture of envelopes, the web of paper is first cut by machine-power, sometimes into rectangular, but more commonly into lozenge or diamond-shaped sheets of large dimensions. These sheets are then placed in convenient piles, and each pile is placed under a series of dies, which are pressed by steam-power down through the pile, thus cutting out a number of very much smaller sheets, termed 'blanks,' of the exact shape of the required envelope, when unfolded and spread out flat. The next process is that of folding and gumming, which is done by hand, or by machine, but chiefly by the latter. In hand-folding, girls fold with wonderful rapidity, having guides to aid them in folding at the proper place; and the gum is applied to the various parts with a small brush. This process is, however, so very slow that it has now been almost superseded by machine folding and gumming. In machine-folding the process is as follows: The blanks are placed in a pile on the front part of the machine, which is self-feeding; the machine being set in motion, the automatic feeder comes forward, and, in lifting the blank, gums the bottom flap, at the same time gumming the upper or open flap, and deposits the blank in an open frame. A plunger descends and forces the blank through the frame to a door. Folders press down the four flaps, fastening the lower one only, the door is lowered, and the envelope is by this action dropped into an endless chain, where it is held in position by means of pins. The envelope then passes through a drying process, and comes out at the other end of the machine ready to be packed up and despatched. The quantity of envelopes that can be made on such a machine is ninety per minute. Where twelve of these machines are working at once, it will be seen that a million envelopes are put out of hand in a very short time. Nearly a million and a half of enveloped letters pass through the post every day in the United Kingdom, most of the envelopes for which are of home manufacture; and besides this, a large export trade is maintained. The stamped envelopes all go to Somerset House, to have the stamp impressed upon them, which is done by a beautiful machine, chiefly invented by Mr Edwin Hill, in which embossing and colour-printing are ingeniously com- bined. These envelopes are sold by the Stamp-office, between which and the Post-office a monetary adjustment becomes necessary.