Experimental arrangement devised by Leopoldo Nobili to study the interference pattern of heat rays. An ebony base carries a thick brass plate to which the other components are fixed. In the middle is a brass screen with two thin slits that can be covered by a sliding brass strip. On one side of the screen is the heat source, which consists of two clamps, probably for holding a glowing wire heated by electrical current. This heating arrangement is controlled by a micrometer screw. A similar arrangement on the other side of the screen supports a second micrometer, to which is secured a rectangular thermopile in a small flat box. The pile has a narrow central slit on one side and two sliding panels forming an aperture of variable width on the other side. The two micrometers allow accurate determination of both the longitudinal and lateral movements of the thermopile. Provenance: Lorraine collections.