Instruments

Polarizing Apparatus

“Of the various apparatuses that are known for polarization of light, there is also one invented by Amici. It was described for the first time in Gerbi’s Corso di Fisica (Vol. 3, page 229, Pisa 1832), [download pdf] who had been informed of it by the author. The Polarizer is no different from the one used by others; but the Analyzer is quite different. It consists of a microscope on the eyepiece of which a rhomboid of Icelandic spar of suitable height is mounted. The pencil of polarized light passing through the rhomboid splits into two beams that pass through two different holes; and when the eye is applied to one or other of these holes it views the field of the microscope entirely illuminated by ordinarily or extraordinarily refracted light. With the addition of a second object-glass, the microscope becomes periscopic and its field suddenly embraces a cone of external light of the considerable amplitude of a hundred and fifty degrees. By this means it is possible to perform the most interesting experiments, and all that is required are tiny crystals or fragments of crystallised substances to show even better all those phenomena that are revealed with larger pieces that are more expensive and more difficult to acquire in a suitable manner” (autographic note by Amici, in A. Meschiari, The microscopes of Giovanni Battista Amici, Tassinari, Firenze 2003).

An accurate description of this instrument also appeared in “Annales de Chimie et de Physique”, Troisième Série, Tome douzième, 1844, p. 114-117 (download pdf), and in “Annalen der Physik und Chemie”, Dritte Reihe, hrsg. von J. C. Poggendorff, Vierter Band, 1845, p. 472-475.

Among the purchasers of Amici’s polarizing apparatus who are registered in the workshop account book (Libro de’ conti del laboratorio) there were (the dates in parentheses refer to the payments):

- Santi Linari, Physics professor at the University of Siena (1833)
- a Prussian Minister (1836)
- the University of Naples bought a number of them from 1836 to 1854
- Giuseppe Belli, Physics professor in the Porta Nuova high school of Milan (1840)
- Pierre Armand Dufrénoy, Director of the Ecole Nationale des Mines in Paris (1845)
- Karl Gotthelf Lehmann, Physiological Chemistry professor in Leipzig (1852)
- Salvadore Gabbrielli, Medicine and Experimental Therapy professor at the University of Siena (1860)
- Bartolomeo Panizza, Anatomist, Surgeon and Physiologist in Pavia (1860)
- The School of Descriptive Anatomy at the S.M.N. Hospital in Florence (1861)

The polarizing apparatus pictured here was constructed by Amici in 1834 for the Physics Laboratory of Luigi Pacinotti at the University of Pisa, where it still is, at the “Centro per la conservazione e lo studio degli strumenti scientifici”.