314 



PRITCHARD S WEDGE PHOTOMETER. 



Setting on Slit (before mounting prism) 0° 0' 0". 

 " D.,* (after " " ) 315° 47' 30". 



Current of Battery = 0.040 Ampere. 

 Reader (alternately) at Circle and Wedge, J. P. 



" at Galvanometer, F. W. V. 

 Object = measurement of transmission of Pritchard wedge for different parts of the spectrum. 

 Time 11.30 a.m. to 2.05 p.m. 



TABLE III. 



->0''.4 



(Dev. 46° 40') 



Mean of Series 1 



-*0''.5 



(Dev. 44° 58') 



Mean of Series 2 



O-'.e 



(Dev. 44° 7') 



Mean of Series 3 



0".' 



(Dev. 43° 37') 



No 

 Wedge. 



Wedge 

 at 0.3 in. 



40.7 



3577 



38.2 



174.0 

 1740 



174.0 



347.0 

 33870 



343.0 



520.0 

 .533:0 



Mean of Series 4 



-♦l^.O 



(Dev. 42° 54') 



Mean of Series 5 



527.0 



822.0 



9.1 

 9.5 



9.3 



47.5 

 50.5 



49.0 



99.0 

 100.0 



99.5 



225.0 

 261.0 



243.0 



504.0 

 454.0 



Wedge 

 at 1.8 in. 



1.5 



1.3 



1.4 



7.4 

 7.1 



7.3 



12.9 

 14.4 



13.7 



61.4 



68.0 



Wedge 

 at 3.3 in. 



64.7 



829.0 479.0 



267.0 

 213.0 



240.0 



1.2 

 1.1 



1.2 



3.3 

 2.3 



2.8 



17.3 

 16.0 



16.7 



Wedge 

 at4 8in. 



137.0 

 122.0 



129.0 



0.7 

 0.4 



0.6 



5.3 

 4.9 



5.1 



65.0 

 62.0 



63.5 



Wedge 

 at 6.3 in 



1.1 



0.7 



0.9 



34.2 

 35.0 



34.6 



PRISMATIC OBSERVATIONS OF -WEDGE TRANSfflSSION OF AUGUST 9, 1886. 

 Extract from Original Record. 



Temperature of Apparatus = 25°.3 C. at 11 a.m. 



State of Sky, milky blue with cumuli. 



Aperture of Slit = 2 mm. (Height of slit is to-day reduced to 11 mm., or slightly less than that 



of the wedge.) 

 Prism used, Hilger No. 3. 



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



Time of a single Yibration = 14 seconds. 



* An optical setting on the sodium line D, is always made as a check on the accuracy of adjustment of the 

 prismatic apparatus. 



