What is the effect upon the condition of pressmen generally by the introduction of the printing-machine to do the heaviest labour of printing? That the trade of a pressman is daily becoming one more of _skill_ than of _drudgery_. At the same time that the printing-machine was invented, one of the principles of that machine, that of inking the types with a roller instead of two large cushions, called balls, was introduced into hand-printing. The pressmen were delighted with this improvement. "Ay," said they, "this saves our labour; we are relieved from the hard work of distributing the ink upon the balls." What the roller did for the individual pressman, the machine, which can only be beneficially applied to rapid and to very heavy printing, does for the great body of pressmen. It removes a certain portion of the drudgery, which degraded the occupation, and rendered it painful and injurious to health. We have seen two pressmen working a daily paper against time: it was always necessary, before the introduction of the machines, to put an immense quantity of bodily energy into the labour of working a newspaper, that it might be published at the proper hour. Time, in this case, was driving the pressman as fast as the rapid stream drove the boatman of the Rhone; and the speed with which they worked was killing them as quickly. CHAPTER XX. Influences of knowledge in the direction of labour and capital--Astronomy--Chronometer--Mariner's compass--Scientific travellers--New materials of manufactures--India-rubber--Gutta-percha--Palm-oil-- Geology--Inventions that diminish risk--Science raising up new employments--Electricity--Galvanism--Sun-light-- Mental labourers--Enlightened public sentiment.