Slowly evolved, the marvelous art, once thoroughly developed, spread with almost lightning rapidity from Mainz throughout the Germanics, the Italian states, France, and England,--in fact, throughout all Christian Europe. It was welcomed by scholars and applauded by popes. Printing presses were erected at Rome in 1466, and book-publishing speedily became an honorable and lucrative business in every large city. Thus, at the opening of the sixteenth century, the scholarly Aldus Manutius was operating in Venice the famous Aldine press, whose beautiful editions of the Greek and Latin classics are still esteemed as masterpieces of the printer's art. The early printers fashioned the characters of their type after the letters that the scribes had used in long-hand writing. Different kinds of common hand-writing gave rise, therefore, to such varieties of type as the heavy black-faced Gothic that prevailed in the Germanics or the several adaptations of the clear, neat Roman characters which predominated in southern Europe and in England. The compressed "italic" type was devised in the Aldine press in Venice to enable the publisher to crowd more words upon a page. [Sidenote: Results of Invention of Printing] A constant development of the new art characterized the sixteenth century, and at least three remarkable results became evident. (1) There was an almost incalculable increase in the supply of books. Under earlier conditions, a skilled and conscientious copyist might, by prodigious toil, produce two books in a year. Now, in a single year of the sixteenth century, some 24,000 copies of one of Erasmus's books were struck off by one printing press. (2) This indirectly increased the demand for books. By lessening the expense of books and enabling at least all members of the middle class, as well as nobles and princes, to possess private libraries, printing became the most powerful means of diffusing knowledge and broadening education. (3) A greater degree of accuracy was guaranteed by printing than by manual copying. Before the invention of printing, it was well-nigh impossible to secure two copies of any work that would be exactly alike. Now, the constant proof-reading and the fact that an entire edition was printed from the same type were securities against the anciently recurring faults of forgery or of error. HUMANISM Printing, the invention of which has just been described, was the new vehicle of expression for the ideas of the sixteenth century. These ideas centered in something which commonly is called "humanism." To appreciate precisely what humanism means--to understand the dominant intellectual interests of the educated people of the sixteenth century --it will be necessary first to turn back some two hundred years earlier and say a few words about the first great humanist, Francesco Petrarca, or, as he is known to us, Petrarch. [Sidenote: Petrarch, "the Father of Humanism"]