6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



10. For example: 



Air temperature 15' 



Pyrheliometer " S. I. Q." 



Reductions 



11. Subtract readings (2) from (i) ; (3) from (4); (6) from 

 <5) ; (7) from (8) ; (10) from (9). 



12. Take the algebraic means 



(i)-(2) + (5)-(6) (5)-(6) + (9)-(io) 



and to them add [(4) — (3)] and [(8) — (7)] respectively. 



13. Call the results above Ri and R,. Find roughly the mean 

 temperatures T^ and To during the intervals of exposure (3) to (4) 

 and (7) to (8). 



14. Add to Ri and R2 the percentage corrections for graduation 

 furnished with the instrument, then, after correcting, add to R^, 

 K[(Ti — 30°)RJ and to R. add lt[T2 — 30°)R2]. K is a con- 

 stant furnished with the instrument. If the prevailing temperature 

 of the air differs much from 20°, add 0.0014R for each 10° the air 

 temperature falls below 20°. The results (which we will call R\ 

 and R'.) are the final rates of rise per 100 seconds during the ex- 

 posures (3) to (4) and (7) to (8) as reduced to the standard bulb 

 temperature of 30°, and standard stem temperature of 20°. 



