In addition to its phantasmatic meaning of ectoplasmic presence, the term spectrum refers to a harmonic composition of a variable quantity over time, whose initial field of study was Newtonian optics and the related experiments on visible light. From Newton to the present day, spectroscopic, -graphic, and -metric practices have been established in many scientific areas, ranging from astronomical to chemical and medical studies. Such fecundity cannot be limited to the field of scientific observation alone but also affects numerous other fields of knowledge and culture. Within this stratified tradition, my contribution intends to focus on a decisive historical moment for spectroscopy—the second half of the 19th century—marked by a theoretical and experimental ferment that follows and justifies the production of the first spectroscopic devices, including those of Fraunhofer (1814) and Kirchhoff-Bunsen (1861). Looking at the rich variety of instruments and applications by leading scientific figures such as Wollaston, Brewster, Talbot, and Janssen, one can note the impact that similar researches had on the manufacture of optical equipment, with particular attention to the dialogue with the instances coming from the photographic world. From this discursive and techno-experimental network spectral images seem to assume the role of mediated articulation of the real, in a manner similar to those doors and grids that Bernard Siegert conceives as cultural techniques. In the case of spectroscopy, such technique is structured along an operation of mediation of the gaze that breaks down and recomposes a harmonious subject, the light, in the attempt to bring out from this fractionating process not an augmentation of the visible, but rather the possible cognitive gaps we have on it.
Matteo Citrini (Wed,) studied this question.