Author: Anna M. Lombardi

Title: The Bolometer and the Spectro-Bolometer, as Steps towards the Black-Body Spectrum

Abstract: My paper would focus on the contribution, afforded in spectroscopy, by the bolometer and the spectro-bolometer, devised in the second half of XIX century by S.P.Langley. This contribution is seen in the framework of an ideal route, following a community of spectroscopists, from researches on the solar constant, to some first attempts to determine the range of wavelengths in which the intensity of solar radiation is mostly concentrated, up to the study of the well-known black body spectrum. It is pointed out the emphasis, laid by Langley on the unification in a single spectral diagram of three curves, then given for "heat", "light" and "actinism"; in this way, it became possible to look for one function, able to represent the behaviour of a source, in infra-red, visible, and ultra-violet ranges, fact that provided a fundamental impulse to the raising of quantum mechanics. In particular, in primary literature about the spectro-bolometer, I looked for signals of transition, from a simpler and more qualitative studying of the spectrum (I mean the individuation of characteristic spectral lines), to a more complete analysis, providing the amount of energy for every single range of radiation.