The ancients had a taste, let us say rather a passion, for the marvellous, which caused them to forget even the sacred duties of gratitude.  Observe them, for example, grouping together the lofty deeds of a great number of heroes, whose names they have not even deigned to preserve, and investing the single personage of Hercules with them.  The lapse of ages has not rendered us wiser in this respect.  In our own time the public delight in blending fable with history.  In every career of life, in the pursuit of science especially, they enjoy a pleasure in creating Herculeses.  According to vulgar opinion, there is no astronomical discovery which is not due to Herschel.  The theory of the planetary movements is identified with the name of Laplace; hardly is a passing allusion made to the eminent labours of D’Alembert, of Clairaut, of Euler, of Lagrange.  Watt is the sole inventor of the steam-engine.  Chaptal has enriched the arts of Chemistry with the totality of the fertile and ingenious processes which constitute their prosperity.  Even within this apartment has not an eloquent voice lately asserted, that before Fourier the phenomenon of heat was hardly studied; that the celebrated geometer had alone made more observations than all his predecessors put together; that he had with almost a single effort invented a new science.

Although he runs the risk of being less lively, the organ of the Academy of Sciences cannot permit himself such bursts of enthusiasm.  He ought to bear in mind, that the object of these solemnities is not merely to celebrate the discoveries of academicians; that they are also designed to encourage modest merit; that an observer forgotten by his contemporaries, is frequently supported in his laborious researches by the thought that he will obtain a benevolent look from posterity.  Let us act, so far as it depends upon us, in such a manner that a hope so just, so natural, may not be frustrated.  Let us award a just, a brilliant homage to those rare men whom nature has endowed with the precious privilege of arranging a thousand isolated facts, of making seductive theories spring from them; but let us not forget to state, that the scythe of the reaper had cut the stalks before one had thought of uniting them into sheaves!

Heat presents itself in natural phenomena, and in those which are the products of art under two entirely distinct forms, which Fourier has separately considered.  I shall adopt the same division, commencing however with radiant heat, the historical analysis which I am about to submit to you.

Nobody doubts that there is a physical distinction which is eminently worthy of being studied between the ball of iron at the ordinary temperature which may be handled at pleasure, and the ball of iron of the same dimensions which the flame of a furnace has very much heated, and which we cannot touch without burning ourselves.  This distinction, according to the majority of physical inquirers, arises from a certain quantity of an elastic imponderable fluid, or at least a fluid which has not been weighed, with which the second ball has combined during the process of heating.  The fluid which, upon combining with cold bodies renders them hot, has been designated by the name of heat or caloric.