250 THOMAS C. BROWN 
similar sands carried for many miles by water or subjected to long- 
continued churning by the waves.* 
A slight elevation of the region, perhaps only a few score feet, 
would allow the sand dunes to migrate out over the Upper Cambrian 
limestones. No elevation of the adjacent land area is necessary 
to account for the transportation of the sand, because the wind 
is well able to transport sand grains of such small size for long 
distances if not interfered with by vegetation. Very slight 
depressions would account for the thin interbedded limestones, and 
a general though gentle submergence of the whole area would 
inaugurate Beekmantown time. 
™ Mackie, ‘““On the Laws That Govern the Rounding of Particles of Sand,” 
Trans. Edinburgh Geol. Soc., VII, 298-311; see also pp. 148-72 (1897). 
