4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 'J2 



place a silvered glass plate (/), each of which glass plates is beveled 

 along its inner edge. These beveled glass edges serve to support the 

 therlo strip in its square form, four around the upper edge of the 

 honeycomb and four around the lower edge. The upper four also 

 serve to determine the area which absorbs radiation. The silvered 

 glass mirror ((7), below the honeycomb, is placed, as shown, at a 

 small angle to the face of the honeycomb and serves both to protect 

 from the wind and to reflect radiation escaping from the lower face 

 of the honeycomb back upon the sides of the tubes. The rod (fc) 

 screws into the plate (/i) and affords a means of mounting the instru- 

 ment in any desired position. The hemispherical shutter, (^), nickeled 

 on the outside and blackened inside, operates from the handle (;'), 

 just as in the pyranometer. The optically figured ultra-violet crown 

 glass hemisphere (rf) serves the same purpose as in the pyranometer 

 arid may be used or not, according to whether or not it is desired to 

 cut off the exchange of long waves between the instrument and the 

 object to which it is exposed. 



The melikeron is similar to the pyranometer in principle. In place 

 of a small flat absorbing surface we substitute a large absorbing area 

 consisting of the above described honeycomb of triangular tubes. 

 Radiation falling normally passes through and is reflected back upon 

 the walls by the rear mirror. Radiation not falling normally strikes 

 the walls of the tubes and after one or more reflections is absorbed. 

 For the purpose of somewhat increasing the blackness of the honey- 

 comb, only the lower two-thirds of each tube is painted with lamp- 

 black, the upper one-third remaining a metallic reflector. Thus the 

 number of regular reflections before final absorption is increased and 

 the loss by diffuse reflection near the upper end reduced, because the 

 diffusely reflecting and radiating lampblack lies so far below the 

 aperture that the latter subtends only a small angular area as viewed 

 from the blackened surface. 



METHOD OF USE 

 For nocturnal radiation, or for the measurement of radiation 

 exchange between the instrument and an object at lower temperature, 

 the melikeron is used like the pyranometer. That is, an electric 

 current is passed into the therlo strip producing heat sufficient to 

 exactly compensate for the loss of heat by radiation. Knowing the 

 current used, the resistance of the strip, and the other constants of the 

 instrument, the amount of heat radiated is computed as with the 

 pyranometer. 



