An Encyclopedia of the History of Technology part 84. This one of a kind encyclopedia presents the entire field of technology from rudimentary agricultural tools to communication satellites in this first of its kind reference source. Following an introduction that discusses basic tools, devices, and mechanisms, the chapters are grouped into five parts that provide detailed information on materials, power and engineering, transportation, communication and calculation, and technology and society, revealing how different technologies have together evolved to produce enormous changes in the course of history | PART FIVE TECHNOLOGY AND SOCIETY Another type of vertical loom used in antiquity was the two-beam vertical loom. This had wooden uprights about 2m high standing vertically. At the top and near the bottom were two horizontal beams. One of these beams usually the top could be adjusted to tension the warp. To warp up this loom the yarn was tied to a bar at the back passed over the top beam down the front of the loom under the bottom beam and up to the bar where its direction was reversed. This gave a pair of yarns at the front for forming the shed. Carpets are still knotted by hand on a similar sort of loom in eastern countries but for weaving cloth it was limited because the shed could not be opened very wide so there was difficulty in passing the weft through. There is much uncertainty about the origins of the horizontal loom in the West. There is no mention of it in Roman literature and there are no pictorial representations earlier than the Middle Ages. It was probably used in China first and spread to Asia Minor during the third to fourth centuries AD. Its advantage lay in having plenty of space where multiple heddles or a draw-cord device could be arranged for weaving figured textiles. Yet textiles with very complex patterns can be woven on the simplest looms by the weaver himself selecting which warp threads are to be raised and which lowered. A sword stick is inserted to keep that shed open while the weft is passed through. Bedouin Arabs still weave strips of carpet in this way. Because it takes a very long time to select each pick not only is it exceedingly painstaking but it is almost impossible to repeat the pattern exactly. THE MIDDLE AGES Carding At some time during the Middle Ages a preparatory process appeared for disentangling the mass of raw wool fibres. It was called carding from cardus the Latin name for a type of thistle or teazle which has small hooks covering its seed heads. The teazle heads were mounted side by side on wooden frames. The carder
