A Manual Of Photography

THERMOGRAPHY. 171 that some purely calorific excitement produces a molecular change, or that a thermo-electric action is induced which effects some change in the polarities of the ultimate atoms of the solid. These are matters which can only he decided by a series of well-conducted experiments ; and, although the subject will not be laid aside by me, I hope the few curious and certainly im- portant facts which I have brought before you will elicit the attention of those whose leisure and well-known experimental talents qualify them in the highest degree for the interesting research into the action of those secret agents which exert so powerful an influence over the laws of the material creation. Although attention was called to tire singular manner in which vapours disposed themselves on plates of glass and copper, two years since, by Dr. Draper, Professor of Chemistry at New York, and about the same time to the calorific powers of the solar spectrum, by Sir John Herschel,1 and to the influence of heat artificially applied, by myself, yet it is certainly due to M. Moser, of Konigsberg, to acknowledge him to be the first who has forcibly called the attention of the scientific world to an inquiry which promises to be as important in its results as the discovery of the electropile by Volta. As to the practical utility of this discovery, when we reflect on the astonishing progress made in the art of Photography since Mr. Fox Talbot published his first process, what may we not expect from Thermography, the first rude specimens of which exhibit far greater perfection than the early efforts of the sister art? As a subject of purely scientific interest, thermography promises to develope some of those secret influences which operate in the mysterious arrangements of the atomic constituents of matter, to shew us the road into the yet hidden recesses of nature’s works, and enable us to pierce the mists which at present envelope some of the most striking phenomena which the penetration and industry of a few “chosen minds" have brought before our obscured visions. In connection with photography, it has made us acquainted with subtile agencies working slowly but surely, and indicated physical powers beyond those which are already known to us, which may possibly belong to a more exalted class of elements, or powers, to which Light, Heat, and Electricity, are subsidiary in the great phenomena of Nature. i Philosophical Transactions, Part I., 1840, p. 50.