Who Established the First Law of Thermodynamics?

Abstract The first law of thermodynamics is believed to have been developed almost simultaneously by Julius Robert Mayer and James Prescot Joule in the 1840s. However, a closer look at history shows that this notion is not tenable. James Watt had a clear vision of energy conversion and conservation. In his 1769 patent, he laid down the foundations for the first law of thermodynamics, which was published in 1774. Watt did not use ordinary language to express his thoughts, but rather drawings that visualized his ideas. In accordance with his understanding of the first law, he conceived the technology of the steam engine.