mould in his foundry caused molten metal to come into contact with cold metal, making the metal surface extremely hard. This process, chilled casting, resulted in what Ransome advertised as "self-sharpening" ploughs. He received patents for his discovery. James Small further advanced the design. Using mathematical methods, he eventually arrived at a shape cast from a single piece of iron, an improvement on the Scots plough of James Anderson of Hermiston. A single-piece cast-iron plough was also developed and patented by Charles Newbold in the United States. This was again improved on by Jethro Wood, a blacksmith of Scipio, New York, who made a three-part Scots plough that allowed a broken piece to be replaced. In 1833 John Lane invented a steel plough. Then in 1837 John Deere introduced a steel plough; it was much stronger than iron designs that it could work soil in US areas previously thought unsuitable for farming. Improvements on this followed developments in metallurgy: steel coulters and shares with softer iron mould boards to prevent breakage, the chilled plough (an early example of surface-hardened steel), and eventually mould boards with faces strong enough to dispense with the coulter. By the time of the early 1900s, the steel plough had many uses, shapes and names. The "two horse breaking plough" had a point and wing used to break the soil's surface and turn the dirt out and over. The "shovel plough" was used to lay off the rows. The "harrow plough" was used to cover the planted seed. The "scratcher" or "geewhiz" was used to deweed or cultivate the crop. The "bulltongue" and "sweeps" were used to plough the middle of the rows. All these metal plough points required being re-sharpened about every ten days, due to their use on rough and rocky ground. Single-sided ploughing The first mould-board ploughs could only turn the soil over in one direction (conventionally to the right), as dictated by the shape of the mould board; therefore, a field had to be ploughed in long strips, or lands. The plough was usually worked clockwise around each land, ploughing the long sides and being dragged across the short sides without ploughing. The length of the strip was limited by the distance oxen (later horses) could comfortably work without rest, and their width by the distance the plough could conveniently be dragged. These distances determined the traditional size of the strips: a