OF ARTS AND SCIENCES. 



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were noted. The whole phenomenon was less distinctly marked than 

 in the case of a single edge ; and the bands of maximum intensity- 

 were not definitely recognizable. It was only with careful attention 

 that even the bands of minimum intensity could be discovered. 



Below are given tables showing the observed and theoretical co- 

 ordinates of the points of interference noted. Table I. is the case of 

 diffraction from a single edge, and Table II. from a narrow obstacle. 



In Table I., the first column gives the distances from the edge of 

 the board measured perpendicularly to its plane : the second and 

 third columns give the observed and calculated abscissas corresponding 

 to these ordinates, for the jjoints of maximum intensity noted ; and 

 the fourth and fifth columns the corresponding values for the points of 

 minimum intensity. 



In Table II., the first column gives the distances from the middle of 

 the board ; the second and third, the observed and theoretical ordi- 

 nates of the first curve of minimum intensity ; and the fourth and fifth 

 columns, the ordinates of the second curve, — all to the right of the 

 middle line ; the sixth, seventh, eighth, and ninth give corresponding 

 values for the two curves to the left of the middle line. 



TABLE I. 



TABLE II. 



