Joule's 1850 paddle-wheel report

Joule's 1850 report describes falling lead weights driving a paddle wheel in a sealed copper vessel of water. The water apparatus has rotating brass arms working between stationary vanes; a boxwood interruption reduces heat conduction along the shaft. The report describes thermometer calibration and resting trials arranged to estimate heat exchanged with the surroundings, alongside the friction trials. These are source-reported apparatus and procedure details, not measurements made for this library.

The water-series tabulation reports a nominal mechanical equivalent of 772.692 in the paper's historical convention: foot-pounds of falling-weight work compared with the heat needed to raise one pound of water by one Fahrenheit degree. The concluding proposition rounds that figure to 772 foot-pounds for raising one pound of water, weighed in vacuo and taken between 55°F and 60°F, by 1°F. Joule states that vibration and sound may make the estimate slightly high. This item adds no modern uncertainty interval or statistical inference. The historical result is empirical evidence from a particular apparatus and correction chain; it does not deductively establish the adopted first-law postulate for all systems.