SMITHSONIAN MISCEI.LANF.OUS COLLECTIONS 



VOL. 66 



From these experiments we see that after definite intervals the 

 deflection due to emission of nocturnal radiation reaches sensibly 

 the same proportions of its final value that occur when heating 

 currents are observed. Hence we may conclude that the true deflec- 

 tion due to the radiation of the sun or the sunlit sky, if such deflec- 

 tions could be observed apart from the secondary cooling efifects 

 described above, would follow the same law of increase with lapse 

 of time as does the deflection due to current. Thus if the one is 

 observed when the first swing is complete, the other should also be 

 so observed to yield comparable results. 



Ow the degree of uniformity of the scale of the Swedish galva- 

 nometer. 



A constant source of electromotive force having been provided, 

 deflections of the galvanometer were observed when the following 

 values formed the total resistances in the galvanometer circuit. 



Resistance in ohms R 



First swing D 



Final deflection D\.. . 



Ratio ,. 



In 



Product DXK 



I2I4 

 20.70 

 17.20 



From these experiments it appears that the first swing is closely 

 proportional to the final deflection for all i)arts of the scale. But 

 the scale is evidently far from uniform, and gives greater sensitive- 

 ness for large deflections. 



On the proportionality betiveen deflection and the square of the 

 heating current applied to the pyranometer. 

 Test made with Swedish galvanometer, reading first swings. 



Current square C'^ 



Deflection D 



Katio yy 



Sensitiveness factor from scale test 5' 



C'-S 

 Product ^ 



.6292 



20.00 



.3146 



251 



788 



