 Steam-powered portable engines and self-propelled traction engines had been introduced for agricultural work from about 1850, but the traction engines were too heavy for direct ploughing of the heavy soil found in Britain.In the 1890s, internal combustion engines started to become more common, but these were stationary engines for belt-driven agricultural machinery.An oil-powered traction engine had been developed, by Hornsby-Ackroyd in 1897, but like the steam-powered traction engines, this was very heavy at 8600 kg (8.5 tons).