20 
MUSEUM BULLETIN NO. 25. 
Sand waves or asymmetrical ripples of mammoth size are 
developed in the Ottawa river during the flood stage over the 
broad sand bar at Duck island. In late summer when these are 
laid bare by low water the crests of the ridges are seen to be 30 
to 45 feet apart and 1 to 2 feet above the troughs. These are 
found on extremely coarse sand. 
R, C. Pierce describes sand waves in the San Juan river, 
California, which are 15 to 20 feet from crest to crest and rise 
3 feet above the troughs. “At one moment the stream is run- 
ning smoothly for a distance of perhaps several hundred yards. 
Then suddenly a number of waves, usually from 6 to 10, appear. 
They reach their full size in a few seconds, flow for perhaps 
two or three minutes, then suddenly disappear. Often for 
perhaps half a minute before disappearing the crests of the waves 
go through a combing movement, accompanied by a roaring 
sound. On first appearance it seems that the waves occupy 
fixed positions, but by watching them closely it is seen that they 
move slowly upstream." 1 The upstream movement of the sand- 
waves doubtless persists only so long as a particular stream 
velocity is maintained. Similar upstream migration of ordinary 
ripple-mark has been observed at a stream velocity of 2.2 
feet per second. 
Examples of large ripple-marks on sand waves were observed 
at Kingsport, Nova Scotia. Their relations to the other feature 
of the beach are indicated in the following excerpt from my notes 
on the Kingsport beach: At low tide the beach exposures at 
Kingsport may be classed in three groups: (1) the rock ledges 
and interspersed stretches of sand and gravel beginning 300 
yards north of the pier and continuing an undetermined distance 
in front of sandstone cliffs to the north; (2) the sandy beach 
extending south from the rock ledges past the pier to the head 
of the tidal ravine and creek district at south side of town; 
(3) the mud and clay beach extending southward from (2) and 
embracing the creek and flats to south. 
The beds forming the irregular floor of (1) are nearly all 
of very coarse Triassic conglomerate including pebbles generally 
§ to 4 inches in diameter. 
1 Water-supply paper 400-C, U.S., Geol. Surv., 1916. 
