8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. '^2 



(3) A rough determination of the constant o- of Stefan's formula 

 was made. A wooden case and water jacket were fitted around Meli- 

 keron No. i to protect it from temperature fluctuations of the sur- 

 roundings. This jacket extended over the face of the instrument, 

 leaving an aperture 3.64 cm. in diameter at 7.03 cm. from the honey- 

 comb face. Two hollow-chamber black bodies were made of double 

 walled galvanized iron vessels (a and h, fig. 5) filled between the walls 

 with stirred water, one at room temperature, the other containing a 

 mixture of ice and water. The melikeron and surrounding jacket 

 just filled the aperture of either of these black bodies, and could be 

 quickly moved from one to the other aperture. The results are sum- 

 marized. Details and necessary corrections which have been intro- 

 duced in these results here will be found in the forthcoming Vol. IV, 

 Annals of the Astrophysical Observatory. 



Value usually accepted (Smith. Phys. Tables, 7, p. 247) 8.26x10-". 



These values are not given as new determinations of sigma. They 

 have little weight for this purpose. They are given to show that not 

 only does the melikeron agree with the standardized pyranometer for 

 short-wave radiation observations but it also agrees well with the best 

 work for long-wave rays. 



Melikeron No. 2. — The constant of this instrument was determined 

 with more care, and by both methods above mentioned, 

 (i) Computed constant. 



Area of aperture formed by beveled glass edges = 2.42 x 



2.42 = 5.86 cm.2 

 Therlo strip =80 cm. long and .003 thick, making an end 



cross-sectional area of 0.24 cm.^ 

 Assume 40 per cent loss by reflection from this edge and 



this correction becomes .096 cm.^ 

 Area of incomplete triangles along edge of aperture = 



0.36 cm.2 

 Radiation entering ■^- this area is lost = o.i8 cm.^ 



