Interference Methods to Astronomical Measurements. 7 



The values of — for which the fringes disappear are 

 a o 

 1-22, 2-24, 3-26, 4*26, &c, 



and the values of the successive (positive or negative) maxima 



are :- 



V = + 1-000 



V = -0-130 



V = +0-065 



V = -0-040 



Here, too, the theory is remarkably well confirmed by ex- 

 periment. This is shown by Table II., in which the letters 

 have the same meaning as before, save that a is now the 

 diameter of the circular aperture. 



Table II. 



s. 



X. a. 



d. 



b. 



/- 



a. 



a v 



e. 



0. 



-1 



s. 



■550 



•701 



20,800 



20-15 



1-22 



6 : 85 



6 ! 94 



-0-09 



c. 



•570 



•200 



20,340 



77-71 



1-22 



1-85 



2-02 



— 



17 



-8 





55 



•271 





51-95 



1-22 



2-76 



2-73 



+ 



03 



+1 





55 



•445 





32-50 



1-22 



4-41 



4-50 





09 



_o 





•445 





52-45 



2-24 



4-52 



4-50 



+ 



02 









„ | -445 





81-45 



3-26 



4-60 



4-50 



+ 



10 



+2 





•701 





20-00 



1-22 



717 



7-09 



+ 



08 



+1 





55 



•701 





34-85 



2-24 



7'55 



7-09 



+ 



46 



+6 





,, 



•701 





52-99 



3-26 



7-14 



7-09 



+ 



05 



+ 1 





,, 



1-000 





25-65 



2-24 



10-20 



10-12 



+ 



08 



+1 





1-000 





14-65 



1-22 



9-77 



10-12 





35 



-4 





„ | 1-000 





27-35 



2-24 



9-63 



10-12 



_ 



49 



-5 





„ : 1-000 





38-55 



3-26 



9-87 



10-12 



— 



25 



_o 





1-230 





21-08 



2-24 



12-47 



12-44 



+ 



03 









1-230 





30-45 



3-26 



12-58 



1244 



4- 



14 



+1 





1-230 





11-15 



1-22 



12-85 



12-44 



■f 



41 



+3 





„ 1 1-230 





21-45 



2-24 



12-23 



12-44 





21 



_2 





„ 1 1-230 





31-15 



3-26 



12-25 



12-44 



_ 



19 



_2 





„ ! 1-230 





39-95 



4-26 



1249 



12-44 



+ 



05 









1-465 





17-42 



2-24 



14-92 



14-82 



+ 



10 



+ 1 





„ , 1-465 





25-99 



3-26 



14-70 



14-82 





12 



-1 





„ 



1-690 





15-14 



2-24 



17-36 



17-10 



+ 



26 



4-2 





„ 



1-690 





23-40 



3-26 



16-36 



17-10 





•74 



-4 



E. 



•623 



0-445 





35-15 



1-22 



4-45 



4-50 



- -05 



-1 



The curve V = A (fig. 3) shows that the maxima are con- 

 siderably smaller than in the case of the slit, and, accordingly, 

 the disappearances are not quite so sharp ; but in one case it 

 was possible to note four of them, and in this case also the 

 average error was less than 2 per cent. 



