The Papers of Joseph Henry

Facsimile of Henry's "Record of Experiments" entry of March 29, 1847, Henry Papers, Smithsonian Archives.


Introdued into the lower part of a flame a piece of mica in the form of a slip of about a tenth of an inch in width[A] this became heated to whitness but when a piece of fine platinum wire was held in the same flame above the mica which was placed edgewise so as not to intercept the ascending flame the heat of the wire was less than when the slip of mica was withdrawn. This experiment was repeated a sufficient number of times to convince me of the truth of the fact. The flame became shorter when the mica was introdued evidently showing from all the results that the effect of the mica was to cool the flame and this was probably due to the increase of radiation.
The principal action of the solid introdued into a flame is to absorbe the heat of the luminous gas which is a bad radiator and an then radiate if freely into space the process is therefore a cooling one to the flame while it heats surrounding bodies.
I am informed within a few days that an account has been going the rounds of the newspapers of a method of saving fuel by mixing clay with the coal. The effect would be produced by the solid radiating into space a part of the heat which would find its way into the chimney.
Flame according to Count Rumford if I recollect aright is a bad conductor of heat[1] and now for the first time in many years a fact arises in my mind which was shown me by a Gentleman in Albany namely when a stove is burning briskly if the damper be shut the pipe around the valve will become red hot in this case the heated air is made to impinge against the side of the tube and thus to impart the heat which would otherwise pass up the chimney.
Make experiments on the heat of different flames.
Henry Papers, Smithsonian Archives.
    [1] Actually Rumford asserted that flame was "a non-conductor of Heat" (italics in original), a claim that was very controversial. Benjamin Thompson, Count Rumford, "Of the Management of Fire, and the Economy of Fuel," Essays, Political, Economical, and Philosophical, 3 vols. (1st American from 3d London ed.; Boston, 1798–1804), 2:65; Sanborn C. Brown, Benjamin Thompson, Count Rumford (Cambridge, Massachusetts, 1979), p. 149.
    [A] Altered from widthth