310 



pritchard's wedge photometer. 



Slit to Bolometer 



5 m. 



Galvanometer, No. 3 (damping magnet at 70 cm.). 

 Time of a single Vibration, 14 seconds. 

 Bolometer, No. 16 (1 mm. aperture). 

 Current of Battery 

 Header at Wedge. J 



0.039 Ampere. 



u 



w 



Watcher ft 

 Object 



measurement of transmission of Pritehard wedge for total solar beam 



If there is no selective absorption, those numbers in the line (b) which express 



should 



the absorption for thicknesses of the wedge differing by equal increments 



be in geometrical progression, and the numbers in the line (c) should represent the 



constant common ratio. These last, on the contrary, increase progressively and 



systematically, and the same evidence of selective absorption is derived from those 



The only 



the following day, August 3, 1886, when they were continued. 



conditions which had changed were : 



Temperature of Apparatus, 20°.2 C. at 10.45 a.m. 

 State of Ski/, excellent blue with occasional cumuli. 



Time 



9.20 to 10.40 a.m. 



TABLE II. 



Time 



9.20 to 10.40 a.m. 



No. Wedge. 



7G5 



739 



(b) 1000 



(c) . . . 



Mean (a) 756 ± 2 



Wedge 

 at 0.3 in. 



336 



322 

 304 

 308 



326 



328 

 325 



320 ± 2 



423.4 



Wedge 

 at 0.8 in. 



147 ± 1 



194.5 



0.459 



Wedge 

 at 3.3 in. 



82.6 



82.3 

 77.2 

 82.2 

 82.3 

 84.8 

 85.2 

 86.5 

 85.4 

 85.4 



110.3 



0.567 



83.4 ± 5 



"Wedge 

 at 4.8 in. 



55.4 

 54.6 

 53.4 



53.0 



56.7 



56.9 

 57.7 

 57.8 

 56.3 

 57.0 



55.9 ± 0.4 



73.9 



0.670 



Wedge 

 at 6.3 in. 



39.8 

 40.3 

 39.0 

 39.5 

 41.7 

 41.2 

 41.9 



41.2 

 42.2 



41.8 



Series 1 



40.9 ± 0.2 



54.1 



0.732 



Series 2 



Series 3 



Series 4 



Series 5 



