THE MELIKERON— AN APPROXIMATELY BLACK-BODY 

 PYRANOMETER 



By L. B. ALDRICH 



INTRODUCTION 



The instrument about to be described is the outgrowth of the 

 experience of Dr. Abbot and myself in the use of the pyranometer, 

 and was planned in many discussions between us, as we walked 

 together to and from the office. The pyranometer (described in 

 Smithsonian Miscellaneous Collections, Vol. 66, Nos. 7 and 11, 

 and Vol. 69, No. 9) has proved of great value in a wide range of 

 radiation measurements. We have long felt the desirability and need, 

 however, of a radiation measuring instrument of equal sensitiveness 

 which would be perfectly absorbing and radiating for all wave- 

 lengths by virtue of its form. Existing types of instruments, such 

 as the pyranometer,' bolometer. Angstrom's pyrgeometer, compensa- 

 tion pyrheliometer, etc., all use a blackened flat surface upon which 

 the radiation falls and is mostly absorbed. For the usual range 

 of wave-lengths, for which the percentage absorption of the blackened 

 surface is well known, these instruments are highly satisfactory. 

 But in measuring radiations from bodies at comparatively low tem- 

 peratures, grave doubt arises [with these instruments] because of the 

 uncertainty of the absorptive power of a blackened flat surface for 

 rays of long wave-length. 



In the new instrument we have tried to produce one embodying an 

 approximately " black-body " absorber, and still to retain as far as 

 possible the advantages of the simple pyranometer. The melikeron 

 is not as sensitive nor as quick-acting as the pyranometer, yet we 

 have been very well pleased with its behavior. A detailed description 

 of the instrument follows. 



DESCRIPTION OF THE MELIKERON 



The name of the instrument, first suggested by Dr. Abbot, is the 

 Greek word /xeXiK^jpoy, honeycomb. That portion of the instrument 

 which absorbs the radiation to be measured is somewhat like a honey- 

 comb in shape. 



Smithsonian Miscellaneous Collections, Vol. 72, No. 13 



