The manuscript volumes of the dark ages were beautiful and magnificent, but their cost was so great that only the most wealthy could buy. A Bible would sometimes cost thousands of dollars. Along in the 14th and 15th centuries Europe began to thirst for knowledge and there arose a demand for cheap books. How could the demand be met? There were now no hordes of intelligent slaves who could be put to work with their pens, and without slave labor the cost of the written book could not be greatly reduced. Invention, as always, came to the rescue and gave the world what it wanted. In the first place, writing material was made cheaper by the invention of paper-making. The wasp in making its nest had given a hint for paper-making, but man was extremely slow to take the hint. The Chinese had done something in the way of making paper from the bark of trees as early as the first century, but it was not until the middle of the 13th century that paper began to be manufactured in Europe from hemp, rags, linen, and cotton. [Illustration: FIG. 9.] In the second place, _printing_ was invented. On a strip of transparent paper write the word _post_. Now turn the strip over from right to left and trace the letters on the smooth surface of a block of wood. Remove the paper and you will have the result shown in Figure 9. With a sharp knife cut out the wood from around the letters. Ink the raised letters and press upon them a piece of paper. You have printed the word "post" in precisely the way the first books were printed. In the 13th century fancy designs were engraved on wood and by the aid of ink the figures were stamped on silk and linen. In the 14th century playing cards and books were printed on engraved blocks in the manner the word "post" was printed above. (Fig. 10.) The block-book was the first step in the art of printing. [Illustration: FIG. 10.--A BLOCK PRINT CONTAINING THE ALPHABET USED BY CHILDREN WHEN LEARNING TO READ.] The block-book decreased the cost of a book, for when a page was once engraved as many impressions could be taken as were wanted, yet it did not meet the necessities of the time. In the middle of the 15th century the desire for reading began to resemble a frenzy and the books that could be got hold of "were as insufficient to slake the thirsty craving for religious and material knowledge as a few rain drops to quench the burning thirst of the traveler in the desert who seeks for long, deep-draughts at copious springs of living water." To meet the demand of the time book-makers everywhere were trying to improve on the block-making process and by the end of the century the book as we have it to-day was being made throughout all Europe.