An Encyclopedia of the History of Technology part 50. 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 THREE TRANSPORT broad steel wheels by ingeniously linked boards pivoted from their peripheries but the real answer to the problem of moving across soft ground was the caterpillar track. As early as 1770 Richard Edgeworth patented a portable railway or artificial road to move along with any carriage to which it is applied . Sir George Cayley also in 1825 took out a patent for an endless chain formed of jointed links which fold themselves round the periphery of two wheels . These patents were perhaps in advance of their time and it was not until the early twentieth century that tracked vehicles moved out of the experimental stage. In America Benjamin Holt of the Holt Tractor Company of California started commercial production of tracked steam-powered tractors in 1904. This firm later became the Caterpillar Tractor Company. In England Ruston Hornsby developed the patent of David Roberts for tracks of separate links joined by lubricated pins. A tractor thus shod was demonstrated to officials of the War Office in 1907 but largely due to the indifference of that authority Rustons sold their patents to Holt. Tracked vehicles were used as artillery tractors first but it was not until 1916 that Winston Churchill then First Lord of the Admiralty ordered the first batch of landships better known by their code name tanks which replaced the earlier water carriers . They were not an immediate success but later came to be an important military weapon see p. 993ff. . After the war the use of tracks became common in earth-moving machines while the internal combustion engine became the standard power unit. Wire ropes and pulleys are still used for raising and lowering long booms such as are used in drag-line and bucket-wheel excavators. However for relatively short lifts as in scraper grader and bulldozer blades or the buckets of dump trucks front-end loaders and back-hoes hydraulic systems have largely superseded rope drive. The first application was by La Plante Choate on the
