Scottish inventor who introduced the use of a hot-air blast instead of a cold-air blast for the smelting of iron, thus greatly advancing the technology of iron production.

In 1817 Neilson was appointed foreman of the Glasgow Gasworks. Soon afterward he became manager and engineer, and he remained with the firm for 30 years.

During the early 19th century, ironworkers in Great Britain believed that a blast of cold air was the most efficient method for smelting iron. Neilson demonstrated that the opposite was true. His idea, first tested at the Clyde Ironworks, Glasgow, was patented in 1828. Use of the hot blast tripled iron output per ton of coal and permitted the profitable recovery of iron from lower-grade ores. It also made possible the efficient use of raw coal and lower grades of coal instead of coke and permitted the construction of larger smelting furnaces.