It has been found by experiment that the performances of new-type dry battery were not inferior to ones of present battery, which has advantages over acetylene black in many aspects.

In the 1910's and 1920's many people "hacked" on crystal sets to take advantage of the new high tech world of radio.

This paper describes the principle, equipments, method and results in the measurement of reflectance of black coating in the electrically calibrated conical cavity radiometer.