Smithsonian Report, 1 9J0. — Wood. 



Plate V. 



V^,^ V::^ M^y \J^ 



vcyOOO 



Fig. 20. 



v^y VQy vq; O O 

 O Q Q O O 



"vT 



v_y v_y v^ v^ v_y 

 v^ v^ v^ V-y v^ 



Fig. 21. 



Photography of Sound Waves. 



