One of the great What ifs of British 20th Century invention, the Malone Heat Engine was a form of Stirling engine, but used liquids operating at the critical point, rather than air. Malone's aim was to build a fuel-efficient marine engine which occupied less space than a conventional steam engine or turbine and boiler, so increasing cargo capacity. The experimental engines built were largely successful, despite the high temperatures and pressures involved requiring ground-breaking solutions - and then the marine diesel became readily available. But has the Malone engine's day now come? 76 well illustrated pages. Paperback. L.A. Mair