218 J. I. Stoddard — Improved Wave Apparatus. 



The following may serve as a guide to the general disposition 

 of the apparatus. Fig. 2. 

 L 



'/ 



L is the arc lamp (if provided with a shade the latter should be transparent) 

 mm, the two mirrors, /the fringes in the focus of the lens /, the eye being at an 

 equal distance on the other side of the lens, Lm may be 100 meters and mf one 

 meter or more. 



The fringes under these conditions appear as a series of fine 

 lines parallel to the intersection of the surfaces db and he. 



If the source be distant and the angle between the mirrors, 

 90 — a, and the wave length, X, then it may readily be shown 

 that the width of the fringes is A/4&. 



Art. XXYIII. — An Improved Wave Apparatus ; by John 



T. Stoddard. 



The apparatus shown in the cuts was made several years ago 

 for the purpose of demonstrating to my classes the formation 



of the compound curves representing the combination of two- 

 simple sound waves. It has answered its purpose so well that 

 a brief description may be of interest. 



