 Beattie was a highly innovative engineer, introducing the country's first successful 2-4-0 locomotive, pioneering feedwater heating, balanced slide valves and coal-burning fireboxes.Since the Rainhill Trials in 1829, it had been accepted that the smoke emitted by burning coal was a nuisance.Railway companies accepted the need to burn coke (a smokeless fuel) in their locomotives, but this was much more expensive than coal, and several locomotive engineers sought a method by which coal could be burned smokelessly.