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SCIENCE PROGRESS 



h 3 = 4. Below are tabulated the sets of parameters which 

 have h 3 equal to 1, as typical of the other sets corresponding to 

 points in the photograph. 



It can be seen how complete the pattern really is, every wave 

 length greater than \ = "034a producing an interference maxi- 

 mum if there are values of h^ h 2 , h 3 to suit. One faint spot is 

 included here which is not in the former table. The vertical and 

 horizontal columns give the values of hi and h 2 respectively. In 



the squares are set the values of — and stars denoting the 



3. 



" magnitude " of the corresponding spot in the photograph, 

 according to an arbitrary scale : 



% * * + • 



Table II 

 h 3 = 1 



Every spot to which can be assigned a value unity of h 3 is 

 represented in this table and it can be seen how complete the 

 scheme is. If, on the other hand, the table had been drawn up 

 on the assumption that when h 3 was unity hx and h 2 could 

 have any integral values without the restrictions explained 

 above, there would be either many unfilled squares or values 

 corresponding to weak spots mixed up with those corresponding 



