Each of those machines, with a boy as an attendant, will fold 2,700 envelopes in an hour, which is nearly the same number that an experienced workman can fold in a day with a folding stick. Notwithstanding the supplanting of manual labour to so great an extent by these ingenious mechanisms, the effect of increased facility of manufacture has been to give increased employment, and many more persons are now engaged in making envelopes than were so employed before the invention of the machines. PRINTING MACHINES. The associated inventions of paper making and printing have progressed hand in hand together; the increased facility with which paper can be made by machinery having been equalled, if not surpassed, by the rapidity with which it can be printed. The old wooden printing press, that was in general use at the beginning of the present century, is now an object of curiosity, and a few specimens of it are to be seen, even in country printing offices. The principal working part of the wooden press consisted of a block of wood, having a perfectly flat and smooth surface, half the size of an ordinary sheet of printing paper, which was brought down upon the types by means of a screw that was turned by a long lever. The types, placed upon a flat stone embedded in a movable table, were inked with large soft balls covered with pelts. The damped paper was put into a frame, at the back of which blankets were placed, and was laid lightly on the inked types. The movable table was then pushed under the block of wood, called the "platten," the long lever was pulled with great strength, and the platten being thus brought forcibly upon the blankets and paper, one-half of the sheet was printed. The lever, on being released, sprang back to its former position, and the table with the types upon it was pushed farther under the platten, which was again pulled down to print the other half of the sheet. The table was then pulled back, and the sheet of paper, printed on one side, was removed. These operations occupied considerable time, and the regular work of two men, with a wooden press, was to print 250 sheets an hour on one side. This original contrivance for printing was supplanted by the Stanhope press, one of the most admirable arrangements for the advantageous application of the lever that is to be found in the whole range of mechanical contrivances.