CONTENTS 21 



PAGE 



and depth of water upon the sand-waves — Sand-waves 

 upon the North Goodwin Sand — Pools left after partial 

 obliteration of sand-waves, similarity of their form to 

 that of the pits called fuljes which occur in sandy 

 deserts. 



Sand-reefs in the Mississippi. 



Their size and movement — Not true transverse waves 

 — Their formation in freshly deposited sediment — How 

 the size of the sand-grains limits the size of the sand- 

 wave — Suggested effect of greater heterogeneity of 

 material to increase the limiting size of the sand-wave 

 — On the relation of velocity of current to size of sand- 

 wave in water of sufficient depth. 



CHAPTER VII 



ON THE SMALLEST DELTA, ON THE COMPOSITION OF QUICK- 

 SAND, AND ON " MACKEREL SKY "... 34O 



On the Transverse and Longitudinal Ridges formed in the 

 Flow of Watery Sand, and on the Smallest Delta. 



Settlement of sand through water and subsidence of 

 water through sand — Transverse and longitudinal ridges 

 formed during the latter process — Rapid deposition of 

 the small longitudinal ridges in radiating branches — 

 Their diameter equal to that of a fully-grown drop of 

 water. 



On the Composition of Quicksand. 



Observations of Mr. C. Carus- Wilson on presence of 

 marsh gas — Experiments of Mr. C. E. S. Phillips on 

 effect of included sas — Author's observations on effect 



