measured and analyzed theoretically for grains of various sizes and 
densities. 
Part II of this report pertains to ripple formation. The term 
ripples is used to indicate the systematic series of undulations or waves 
that are observed to form an the bed at certain critical velocities. 
Natural ripples are formed at velocities greater than those required for 
general movement, where natural ripples are those generated directly on a 
smooth bed by the intense movement of the particles, and not by conspic- 
uous external obstructions which tend to hasten their formation even at 
much lower velocities. It was the objective of the explanation in this 
part of the report to examine the phenomenon of natural ripple formation. 
In this study experimental observations were limited to the initial 
formations of the natural ripples and as such experimental analysis was 
limited to that stage. 
This report will be published as a Technica] Memorandum of the 
Beach Erosion Board during the summer of 195k. 
III. University of California, Contract No. DA-l9-055-eng-31, Status 
Report No. 2 - 1 Nov to 31 Jan 195). 
1. The installation and calibration of instruments for measuring 
waves, Wind, pressure drop and wind tides has been completed. 
Bo The following measurements are made for each experimental run: 
a. The wind set-up at 5 locations along the center line of 
the channel. 
b. The vertical wind velocity distribution at 3 locations in 
the channel by use of a pitot tube. 
c. Wave measurements at 4 locations along the channel. At 
each of these 4 points of measurement a continuous surface 
time history is obtained over a time period of approximately 
one hour so that it is possible to evaluate the data for 
mean, significant and meximum waves as a function of the 
duration of the wind. 
3. Experiments in progress involve the following wind and channel 
conditions: 
a. Five different average wind velocities. 
b. Seven different still-water depths. 
ce All the above mentioned conditions are to be conducted for 
both rough and smooth bottoms of the channel. 
IV. Scripps Instituticn of Oceanography, Vontract No. DA-49-055-en 
Quarterly Progress Report No. 18 - Oct. to Dec. 1953. 
-3, 
The variability of orbital velocities is being compared with the 
variability of the waves generating them. Comparisons are made from 
20-minute records which represent widely different conditions. 
10 
