Editing History of physics (section)

===Thermodynamics===
During the 18th century, thermodynamics was developed through the theories of weightless [[imponderable fluid|"imponderable fluids"]], such as heat ("caloric"), [[electricity]], and [[phlogiston theory|phlogiston]] (which was rapidly overthrown as a concept following [[Antoine-Laurent Lavoisier|Lavoisier's]] identification of [[oxygen]] gas late in the century). Assuming that these concepts were real fluids, their flow could be traced through a mechanical apparatus or chemical reactions. This tradition of experimentation led to the development of new kinds of experimental apparatus, such as the [[Leyden Jar]]; and new kinds of measuring instruments, such as the [[calorimeter]], and improved versions of old ones, such as the [[thermometer]]. Experiments also produced new concepts, such as the [[University of Glasgow]] experimenter [[Joseph Black]]'s notion of [[latent heat]] and Philadelphia intellectual [[Benjamin Franklin]]'s characterization of electrical fluid as flowing between places of excess and deficit (a concept later reinterpreted in terms of positive and negative [[electric charge|charges]]). Franklin also showed that lightning is electricity in 1752.

The accepted theory of heat in the 18th century viewed it as a kind of fluid, called [[caloric theory|caloric]]; although this theory was later shown to be erroneous, a number of scientists adhering to it nevertheless made important discoveries useful in developing the modern theory, including [[Joseph Black]] (1728–1799) and [[Henry Cavendish]] (1731–1810). Opposed to this caloric theory, which had been developed mainly by the chemists, was the less accepted theory dating from Newton's time that heat is due to the motions of the particles of a substance. This mechanical theory gained support in 1798 from the cannon-boring experiments of Count Rumford ([[Benjamin Thompson]]), who found a direct relationship between heat and mechanical energy.

While it was recognized early in the 18th century that finding absolute theories of electrostatic and magnetic force akin to Newton's principles of motion would be an important achievement, none were forthcoming. This impossibility only slowly disappeared as experimental practice became more widespread and more refined in the early years of the 19th century in places such as the newly established [[Royal Institution]] in London. Meanwhile, the analytical methods of rational mechanics began to be applied to experimental phenomena, most influentially with the French mathematician [[Joseph Fourier]]'s analytical treatment of the flow of heat, as published in 1822.<ref>{{Harvtxt|Heilbron|1979}}</ref><ref>{{Harvtxt|Buchwald|1989}}</ref><ref>{{Harvtxt|Golinski|1999}}</ref> [[Joseph Priestley]] proposed an electrical inverse-square law in 1767, and [[Charles-Augustin de Coulomb]] introduced the inverse-square law of [[electrostatics]] in 1798.

At the end of the century, the members of the [[French Academy of Sciences]] had attained clear dominance in the field.<ref name="Guicciardini1999" /><ref>{{Harvtxt|Greenberg|1986}}</ref><ref>{{Harvtxt|Guicciardini|1989}}</ref><ref>{{Harvtxt|Garber|1999}}</ref> At the same time, the experimental tradition established by Galileo and his followers persisted. The [[Royal Society]] and the [[French Academy of Sciences]] were major centers for the performance and reporting of experimental work. Experiments in mechanics, optics, [[magnetism]], [[static electricity]], [[history of chemistry|chemistry]], and [[physiology]] were not clearly distinguished from each other during the 18th century, but significant differences in explanatory schemes and, thus, experiment design were emerging. Chemical experimenters, for instance, defied attempts to enforce a scheme of abstract Newtonian forces onto chemical affiliations, and instead focused on the isolation and classification of chemical substances and reactions.<ref>{{Harvtxt|Ben-Chaim|2004}}</ref>

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