The book covers over 100 years of tractor development and features more than 100 different tractors. The first steam engines on wheels which used belts to drive farm machinery developed into traction engines, used on farms by pulling a plough on cables between two engines. In the 20th century, stationary internal combustion engines, such as the Clutterbuck, began to be put on wheels and moved around a farm to drive threshing machines by belt. Dozens of small companies grew up around the world following their own lines of development. Most lasted only a short time. Firms like Allis-Chalmers, Benz, Lloyd, Jelbart, Glasgow, Fordson, Bates and Hart-Parr are famous names which have faded away or been taken over. A few companies, such as Case and Massey, started in the middle of the 19th century and continue today on a global scale. John Deere started making ploughs in 1837 and is now the largest manufacturer in the world. Some developments have caused a giant leap forward: the use of rubber pneumatic tyres rather than metal wheels; turbo-charged diesel engines and the hydraulic three-point hitch system designed by Ferguson, which is still used today in some form on most modern machines. All are photographed here, many in action and in different countries.