"The older view of the nature of heat was that it is a substance, very fine and imponderable indeed, but indestructible, and unchangeable in quantity, which is an essential fundamental property of all matter"

The quote by Hermann von Helmholtz is describing the older view of heat as a substance. This view recommends that heat is a very great and imponderable product, suggesting it is unable to be weighed or determined. It is also indestructible, suggesting it can not be damaged, and unchangeable in amount, implying it can not be increased or decreased. This view suggests that heat is an important basic home of all matter, suggesting it is a needed part of all matter and can not be separated from it. This view of heat was extensively accepted till the 19th century when the principle of energy was established and the concept of heat as a type of energy was presented. This brand-new view of heat as energy replaced the older view of heat as a substance.