Witnessing Power: John Elder and the Making of the Marine Compound Engine, 1850–1858

Shipowners’ seemingly slow adoption of marine compound engines is often attributed to not appreciating the new technology’s superior economy. This article argues that this slow adoption needs to be understood alongside the challenges faced by engine builders in persuading skeptical shipowners and practical engineers that their designs were trustworthy. It explores the rich cultural contexts within which Glasgow master engineer John Elder and his associates rendered their marine compound engines credible for Liverpool’s Pacific Steam Navigation Company, the first line to deploy the new engine. Elder operated within a culture whose hallmarks were useful work, economy, and the power of direct witnessing. The article also explores the role of William McNaught, an independent consultant with a strong track record as both a practical engineer and the inventor of a steam-engine indicator. His indicator, deployed to evaluate the performance of Elder’s compound engines, stood at the center of the controversy over their economy.