RECENT AND FOSSIL RIPPLE-MARK. 
17 
sand; but the surface may still show graining in the line of the 
current. Much depends, however, on whether sand is or is not 
being deposited from above; since, when it is, ripples are pro- 
duced at a somewhat lower velocity and advance more quickly. 
These results applied to the case of water varying from 1 to 8 
inches in depth, and might be very different in the case of much 
deeper water. I have long felt that such experiments ought to be 
conducted on a much larger scale but had never had the oppor- 
tunity in a suitable and convenient place, free from disturbance. 
In the present state of the subject it may be assumed that, in 
the case of moderately fine sand, the well-developed ripple- 
drift, so common in certain rocks, indicates a current with a mean 
velocity of about 1 foot per second.” Owen 1 has also investi- 
gated the relations which exist between ripple-mark formation 
and current velocity. That portion of his table relating to 
ripple-mark follows : 
Nature of bottom. 
Depth in 
inches. 
Velocity of current. 
Miles 
per hour. 
Feet 
per second. 
Rippled sand 
1 
0-91 
1-33 
Rippled sand 
2 
0-92 
1-35 
Rippled sand, soft. 
3 
1-20 
1-76 
Rippled sand, very soft. ...... 
Fine sand moving in a sheet, not 
5 
1-50 
2*20 
rippled. 
3* 
1-70 
2-50 
Sand moving in a sheet, not rippled 
3 
1-84 
2-7 
Sand moving in a sheet, no ripples. 
3 
2*18 
3-20 
A favourable locality for observing the correlation of 
current velocity with the formation or non-formation of ripple- 
mark was found in the Avon river a half mile above the railway 
bridge at Windsor, Nova Scotia. There at low tide a section 
of the river about 125 feet long by 45 feet wide flows over a 
stretch of sand with very uniform slope but with sufficient 
grade to give a strong current; a good opportunity is afforded to 
observe the successive formation of a series of ripple-mark 
1 1 "Experiments on the transporting power of sea currents,” Geog. Jour., vol. XXXI, 
1908, pp. 415-420. 
