356 WAVES OF SAND AND SNOW 



is an emulsion of all three. I think it is probable 

 that the inclusion of ordinary air often makes wet 

 sands unable to bear a load. 



I made the following observations upon the 

 air imprisoned in wet sand at the foot of 

 the East Bournemouth cliffs when I was examining 

 miniature deltas and mud-flows. In one place 

 somewhat muddy sand had flowed, with production 

 of wealds or transverse ribs, and had come to rest. 

 The surface was dry, but quaked under foot. I 

 found an empty beer-bottle lying on the beach, 

 and, holding it by the neck, I used the bottom 

 as a plunger, inserting it in the sa'nd and pushing 

 it up and down without withdrawing it. Numerous 

 large bubbles of air came up, and after a time 

 the bottle was gripped and held pretty tightly by 

 the sand. Near by was an alluvial fan, or delta- 

 like deposit, where the sand was purer, containing 

 much less admixture of fine, earthy particles. It 

 had flowed with less formation of broad wealds 

 and more of the longitudinal ridges already de- 

 scribed, which are due to the rapid separation of 

 sand from water. In this deposit I inserted the 

 plunger and worked it up and down as before. 

 Some bubbles of air came up, but they were few 

 in number and small in size. I should add that 

 in both cases the working of the plunger produced 



