OF ARTS AND SCIENCES. 



271 



were noted. The whole iihonomeiiou was less distinctly niarkcfl than 

 iu the case of a single edge ; and the bands of maxinmni intensity 

 were not definitely recognizable. It was only with careful attention 

 that even the bands of mininnun intensity could be discovered. 



Below are given tjxbles showing the observeil 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 points 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 IL 



