101 
Museum Bulletin No. 25. 
Plate XXIII. 
A. Interference ripple-mark in a shallow pond, Hamilton county, Ind. 
(Pages 34, 36.) 
B. Interference ripple-mark photographed in shallow water, Britannia, Ont. 
Photograph by L. D, Burling. (Page 34.) 
C. Plaster cast, taken under water, of interference ripple-mark, Britannia, 
Ont. (Pages 34, 35.) 
