Concerning

the Radical Decomposition of Bodies,

especially of Metals.

The objective cause of the sensation known by the name of light — is light-matter original: "Lichtstoff." In the 18th century, many natural philosophers believed light, heat, and fire were composed of "subtle fluids" or material particles rather than being purely energetic waves or reactions..

The objective cause of the sensation known by the name of heat, is only heat-matter original: "Wärmestoff." This refers to the "caloric" theory, which viewed heat as a fluid that flowed from hotter to colder bodies..

The objective cause of the phenomenon known by the name fire, is never fire-matter original: "Feuerstoff." The author is notably rejecting the "phlogiston" theory here, which posited that fire was a material substance contained within combustible bodies and released during burning..

These three causes of the three phenomena of light, heat, and fire can be considered either in their actual manifestation, or in their state of rest.

In the first case, the product becomes sensible light, sensible heat, sensible fire.