352 WAVES OF SAND AND SNOW 



tongue of sand is strongly curved, and its tip is 

 often distinctly drop -like. The diameter of the 

 tongue is commonly | inch, which I find is abbut 

 the width of the larger drops in which rain collects 

 on the under side of the sash of a window. The 

 size and form of the thread-like stream of water 

 is, in fact, due to capillarity, and the size and 

 cross -section of the little tongues of sand which 

 it deposits are therefore determined by the same 

 force. The breadth of the smallest delta is there- 

 fore the diameter of a full-sized drop of water. 



On the Composition of Quicksand. 



A quicksand is one which readily swallows any 

 heavy body placed upon it. Dr. J. C. Owens has 

 shown experimentally how this condition can be 

 brought about by allowing water to flow upwards 

 through the sand.i Since, he says, a grain of 

 siliceous sand of 5V in. diameter settles through 

 water at the rate of little more than 02 foot per 

 second, a very slight velocity of current is capable 

 of lifting the grains out of contact and keeping 

 them separated by layers of water, so that they 

 will not bear weight. In Nature, Dr. Owens says, 

 such quicksands are due to springs finding an outlet 



'' " The Transport and Settlement of Sand in Water, etc.," 

 Section 9, British Association, Birmingham, 1913. 



