Visible and Invisible
The chemical action of light, so far from being confined to the most refrangible rays, we now know extends over the whole spectrum, visible and invisible, the action only being shifted from one ray to another, according to the substance upon which its peculiar functions are exerted. It is extremely difficult to explain many of the phenomena of light by either of the rival theories; and as we proceed in our inquiries, the question of the materiality or immateriality of light becomes more and more complicated. A matter of much interest arises out of these considerations, which is, are the different rays in similar electrical states, or do they vary in this respect with their refrangibility? Those philosophers who have adopted the undulatory theory of light, put the question aside with a smile, or show how completely the electrical notion is at variance with their theory. There exist many very great difficulties in solving this problem, but although a good theory will often aid us in discovering the truth, we must not allow our researches to be stopped, because they may appear inconsistent with the received notion. If we could establish the fact of a peculiar electrical action existing in the different rays of light, we should then have the means of reducing to something like a system, the many anomalous features which come under our notice in prosecuting our studies into the character of the solar system. “In this instance, says M. Arago, “it is upon the unforeseen that we are especially to reckon,” and every new discovery goes to prove the correctness of this. (Robert Hunt, A Popular Treatise on the Art of Photography (1841) 91-92)
The conflict between wave and particle theories of light continued across the 19th century, and photography was thrust in the middle. Though wave theory dominated, more atomistic approaches are found in many writings, particularly Oliver Wendell Holmes writings on the stereograph.
This is important to me because the “identity” of photography which emerges in scientific approaches seems to point at its ability to extend vision, while the identity prevalent in aesthetic discourse points at its it limitations when applied to human affairs. This is one of many binary divisions which are neither intuitive nor uncomplicated in discussions of photography’s status as evidence.
