"Ritchie's Apparatus. To show the relation of radiation and absorption. Consisting essentially of a differential thermometer, with reservoirs of metal, the face of one black with lampblack, that of the other covered with white paint. A stand carrying a cylindrical vessel is placed between the arms, and can be adjusted to any desired position. This vessel is filled with hot water, and has its face, which is opposite the reservoir with blackened face, covered with white paint, and that opposite the one covered in white paint blackened with lampblack. Thus, the radiation from the black surface is absorbed by the white, and vice versa, ...$20.00"

   The apparatus is thus a combination of Leslie's Cube and the Differential Thermoscope. 

   It is the collection of John Badner, who also supplied the picture.