Interference Methods to Astronomical Measurements. 5 



Table I. shows well the accordance between theory and ob- 

 servation. Under S is given the nature of the light used : 

 S denotes sunlight, C calcium light, R red light. 



The other quantities given in the Table are : — 



X = Approximate wave-length in thousandths of a milli- 

 metre. 



a = Width of slit by direct measurement. 



d = Distance to telescope. 



b = Distance between centres of slits. 



/ = Factor depending on the order of the observed dis- 

 appearance. 



a = Angle deduced from the observations. 



e 

 o 



d 



x 206265", 



Error in seconds. 

 Error per cent. 



Table I. 



s. 



X. 



a. 



d. b. 



/■ 



a. 



a v 



e. 



0. 



s. 



•550 



•240 



20,800 



50-15 



1-00 



2-26 



2-38 



-012 



— 5 



,, 





•490 



5) 



23-35 



1-00 



4-86 



4-85 



4-0-01 







,, 





•740 



'5 



15-45 



1-00 



7-33 



7-33 



■00 







c. 



•570 



•197 



20,340 



65-75 



1-00 



1-78 



1-99 



- -21 



-10 



,, 





•365 



,, 



65-75 



2-00 



3-57 



3-69 



- 42 



- 3 



,, 





•547 



,, 



65-75 



3-00 



5-35 



5-53 



- 18 



- 3 



55 





•723 



I 65-75 



4-00 



7-14 



7-31 



- 47 



— 2 



,, 





•900 



1 65-75 



5-00 



8-92 



9-11 



- 49 



- 2 



,, 





•238 



' 53-75 



1-00 



2-18 



2-41 



- -23 



-10 



,, 





•442 





53-75 



2-00 



4-36 



4-47 



- -11 



- 3 



,, 





•650 



55 



53-75 



3-00 



6-55 



6-58 



- -03 







„ 





•865 



„ 



53-75 



4-00 



8-73 



8-75 



- -02 







,, 





1-105 



55 



53-75 



5-00 



10-91 



11-18 



- -27 



- 3 



,, 





•277 





40-75 



1-00 



2-88 



2-80 



+ -08 



+ 3 



55 





•567 



,, 



40-75 



2-00 



5-76 



5-74 



-f -02 



55 





•858 



,, 



40-75 



3-00 



8-64 



8-68 



- -04 



„ 





1-150 



j, 



40-75 



4-00 



11-52 



11-64 



- 42 1 - 1 



,, 





1-412 





40-75 



5-00 



14-40 



14-28 



4- -12 +1 



„ 





•388 



, 



31-15 



1-00 



377 



393 



- -16 



- 4 



,, 





•757 



55 



31-15 



2-00 



7-54 



7-66 



- -12 



_ o 



„ 





1-160 





31-15 



3-00 



11-31 



11-73 



- -42 



- 4 



„ 





1-532 





31-15 



4-00 



15-08 



15-40 



- -32 



_ 9 



,, 





1-902 



M 



31-15 



5-00 



18-85 



19-25 



- 40 



o 



E. 



•623 



•298 



J? 



44-75 



1-00 



2-86 



3-02 



- 46 



— n 



,, 





•573 





44-75 



2-00 



5-73 



5-80 



- -07 



- 1 



55 





•852 



„ 



44-75 



3-00 



8-65 



8-62 



4- -03 







,, 





1-108 



„ 



44-75 



4-00 



11-46 



11-21 



4- -25 



+ 2 



»S 





1-415 



f} 



44-75 



5-00 



14-32 



14-32 



00 







5? 





1-672 



„ 



44-75 



6-00 



17-18 



16-92 



+ -26 



+ 2 



J5 





1*945 



„ 



44-75 



7-00 



20-05 



19-69 



+ -36 



+ 2 



" 



" 



2-223 



1 



, 



44-75 



8-00 



22-91 



22-49 



+ -42 +2 



