* 1802 – Joseph Louis Gay-Lussac publishes Charless law, discovered (but unpublished) by Jacques Charles around 1787; this shows the dependency between temperature and volume. Gay-Lussac also formulates the law relating temperature with pressure (the pressure law, or Gay-Lussacs law)
* 1804 – Sir John Leslie observes that a matte black surface radiates heat more effectively than a polished surface, suggesting the importance of black-body radiation
* 1805 – William Hyde Wollaston defends the conservation of energy in On the Force of Percussion
* 1808 – John Dalton defends caloric theory in A New System of Chemistry and describes how it combines with matter, especially gases; he proposes that the heat capacity of gases varies inversely with atomic weight
* 1810 – Sir John Leslie freezes water to ice artificially
* 1813 – Peter Ewart supports the idea of the conservation of energy in his paper On the measure of moving force; the paper strongly influences Dalton and his pupil, James Joule
* 1819 – Pierre Louis Dulong and Alexis Thérèse Petit give the Dulong-Petit law for the specific heat capacity of a crystal
* 1820 – John Herapath develops some ideas in the kinetic theory of gases but mistakenly associates temperature with molecular momentum rather than kinetic energy; his work receives little attention other than from Joule
* 1822 – Joseph Fourier formally introduces the use of dimensions for physical quantities in his Théorie Analytique de la Chaleur
* 1822 – Marc Seguin writes to John Herschel supporting the conservation of energy and kinetic theory
* 1824 – Sadi Carnot analyzes the efficiency of steam engines using caloric theory; he develops the notion of a reversible process and, in postulating that no such thing exists in nature, lays the foundation for the second law of thermodynamics, and initiating the science of thermodynamics
* 1827 – Robert Brown discovers the Brownian motion of pollen and dye particles in water 
* 1831 – Macedonio Melloni demonstrates that black-body radiation can be reflected, refracted, and polarised in the same way as light
* 1834 – Émile Clapeyron popularises Carnots work through a graphical and analytic formulation. He also combined Boyles Law, Charless Law, and Gay-Lussacs Law to produce a Combined Gas Law.  PV/T = k 
* 1841 – Julius Robert von Mayer, an amateur scientist, writes a paper on the conservation of energy, but his lack of academic training leads to its rejection
* 1842 – Mayer makes a connection between work, heat, and the human metabolism based on his observations of blood made while a ship's surgeon; he calculates the mechanical equivalent of heat
* 1842 – William Robert Grove demonstrates the thermal dissociation of molecules into their constituent atoms, by showing that steam can be disassociated into oxygen and hydrogen, and the process reversed
* 1843 – John James Waterston fully expounds the kinetic theory of gases, but according to D Levermore "there is no evidence that any physical scientist read the book; perhaps it was overlooked because of its misleading title, Thoughts on the Mental Functions."
* 1843 – James Joule experimentally finds the mechanical equivalent of heat 
* 1845 – Henri Victor Regnault added Avogadro's Law to the Combined Gas Law  to produce the Ideal Gas Law. PV = nRT
* 1846 – Grove publishes an account of the general theory of the conservation of energy in On The Correlation of Physical Forces 
* 1847 – Hermann von Helmholtz publishes a definitive statement of the conservation of energy, the first law of thermodynamics