In his chapter on “Radiation” (1865) in Fragments of Science: A Series of Detached Essays, Addresses, and Reviews, Tyndall described a diagram drawn by a Professor Müller, which showed the distribution of heat in the spectrum of electric light, as follows:
In the region of the dark rays, beyond the red, the curve shoots up to B, in a steep and massive peak – a kind of Matterhorn of heat, which dwarfs the portion of the diagram CDE, representing the luminous radiation. Indeed the idea forced upon the mind by this diagram is that the light rays are a mere insignificant appendage to the heat-rays represented by the area ABCD, thrown in as it were by nature for the purpose of vision.(1)
Tyndall further refers to the “summit of the peak representing the sun’s invisible radiation” and the “mountain of invisible heat.” As I have mentioned before, the Tyndall letters I will be transcribing concern his time mountaineering in the Alps in the mid-nineteenth century. So I enjoyed seeing his use of “Matterhorn,” “peak,” “mountain,” and “summit” when describing the diagram, a reflection of his two passions: physics and mountaineering.
I have my first disc of letters to transcribe, but I will begin working on those next week. In the meantime, more reading for background on Tyndall.
(1) Tyndall, John. Fragments of Science: A Series of Detached Essays, Addresses, and Reviews. Vol. 1. New York: Appleton and Company, 1897, p. 44.