Primary Discourse

PRIMARY causes are:

• unknown to us
• subject to simple and constant laws

These laws:

• may be discovered by observation
• are the object of natural philosophy.

Heat, like gravity, penetrates every substance of the universe.

• Its rays occupy all parts of space.

I lay down the mathematical laws obeyed by this element.

The knowledge of rational mechanics, which the most ancient nations had been able to acquire, has not come down to us, and the history of this science, if we except the first theorems in harmony, is not traced up beyond the discoveries of .

Archimedes was a great geometer who explained the mathematical principles of the equilibrium of solids and fluids.

Galileo was the originator of dynamical theories.

• He discovered the laws of motion of heavy bodies.

Within this new science Newton comprised the whole system of the universe.

The successors of these philosophers have extended these theories, and given them an admirable perfection: they have taught us that the most diverse phenomena are subject to a small number of fundamental laws which are reproduced in all the acts of nature. It is recognised that

The same principles regulate all:

• the movements of the stars, their form, the inequalities of their courses
• the equilibrium and the oscillations of the seas
• the harmonic vibrations of air and sonorous bodies
• the transmission of light, capillary actions, the undulations of fluids
• the most complex effects of all the natural forces

Thus has the thought of Newton been confirmed.

But these mechanical theories do not apply to the effects of heat.

Heat makes up a special order of phenomena, which cannot be explained by the principles of motion and equilibrium.

I have the laws for heat from prolonged study and attentive comparison of the facts known up to this time.

To create this theory, I precisely distinguished and defined the elementary properties which determine the action of heat.

I then perceived that all the phenomena which depend on this action resolve themselves into a very small number of general and simple facts.

Every physical problem of this kind is brought back to an investigation of mathematical analysis.

From these general facts I have concluded that to determine numerically the most varied movements of heat, it is sufficient to submit each substance to three fundamental observations.

Different bodies do not have the same degree the power to:

• contain heat
• receive or transmit it across their surface
• conduct it throughout the interior of their masses.

These are the 3 specific qualities which my theory clearly distinguishes and shews how to measure.