THE ATMOSPHERE AS A GEOLOGICAL AGENT. 



27 



The incipient stages of dune formation are readily seen in many 

 dry, sandy regions. The dune is hkely to start in the Ice of some ob- 



Fig. 8. — Dune ridges parallel to the direction of the wind. Southwest part of India. 

 Scale about 3 miles to the inch. (Cornish.) 







^H/ 



Fig. 9. — Dune ridges transverse to the direction of the wind. Scale about 3 miles 



to the inch. (Cornish.) 



stacle, and to be elongate in the direction of the wind, especially if 

 the wind be strong relative to the supply of sand. This shape is per- 



