Brass bar fixed to a base of mahogany wood.
It is a simple optical bench used by Melloni to study the laws of the distribution of radiating heat.
Functioning:
On the bar could be set various components, including lenses, light and heat sources, thermoelectric piles etc. It is used for experiments on radiation, refraction, absorption and reflection of heat.
Macedonio Melloni was a famous Italian physicist of the early nineteenth century.

See also:
http://www.museodifisica.unina.it/eng_coll_melloni.htm#