The object of these experiments was to compare together the radiations from the polished surfaces of different bodies, all having the temperature of 212°. In order to heat the bodies, a tin box was used, double-sided and double-bottomed, or a box within a box. Water being kept boiling in the interval, the interior chamber was found to have a temperature of nearly 212°; and on the bottom of this chamber the bodies to be experimented on were placed. When being used these were taken out of the chamber and placed before the sentient pile of a thermo-multiplier, the galvanometer needle connected with which was immediately deviated from its zero position.