Putting steam engines on ships happened around the same time, but it was not until the second half of the 1800s, and the invention of the screw propeller to replace the paddle wheel, that ocean-going steam could challenge sail for price as well as speed. Sailing technology peaked in the late 1860s with the launch of the Cutty Sark and other fast clippers. The story of the screw propeller shows all the usual elements of an innovation: a long prehistory, simultaneous breakthroughs by two rivals, then incremental evolution over many years. The idea had actually been around since the 1600s and it
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