358 THE POPULAR SCIENCE MONTHLY. 



are small ; some of them exceedingly minute. We found, in spe- 

 cimens of drifted sand, 1,920 particles in the weight of a troy grain. 

 This will give, for a pound avoirdupois, more than 13,000,000, and 

 about 1,450,000,000 in a cubic foot of sand. The comparison of a 

 "great multitude" to the "sands of the sea-shore" is wonderfully 

 vivid and impressive. Examined by the aid of a microscope, these 

 delicate grains are seen to have lost the sharp, angular features of 

 broken quartz, and closely resemble pebbles, irregular in form, but 

 smooth and rounded. They are wave-worn bowlders on a small scale. 



This beach, which is seldom more than one-third of a mile broad, 

 constitutes the coast-line from Coney Island at the entrance to New 

 York Harbor, to the Nepeague Hills, a distance of about one hundred 

 miles, but broken by occasional inlets through which the tides ebb 

 and flow. Throughout this distance, scarcely a pebble of any consid- 

 erable size occurs. Mather, in the " Geological Survey of the State 

 of New York," commenting on this magnificent beach-line, says, " In 

 Europe, there is no deposit of a similar character to compare with it 

 in extent." 



Eastward from the Nepeague hills, which are of sand, along the 

 ocean-side of Montauk Point, high bluffs of bowlder-drift reach the 

 shore, strewing it with their falling debris. Here may be seen on a 

 grand scale the process by which rocks are transformed into the fine 

 sand of which the beach is composed. The waves throw their whole 

 force upon the shore, carrying forward with tremendous roar tons of 

 bowlders and pebbles which roll back as the waves recede. This pro- 

 cess is repeated with every wave. The stones thus rolled and tossed 

 lose something of their volume, and scarcely one can be found that 

 does not show signs of disintegration and decay. All of them are 

 penetrated by moisture, some are fractured by frost, and others, weak- 

 ened by chemical changes, are dashed in pieces. The sand-beach rep- 

 resents the silicious matters of these comminuted rocks. Its position 

 along the coast is determined by the set of the waters, but its contour 

 of sand-hills is determined by winds. These, in their endless play, 

 have carved it into every form possible to drifting sands. Mather 

 observed that " where the beach is above the reach of the surf, it is 

 covered by a labyrinth of hillocks of drifting sand, imitating almost 

 all the varieties of form which snow-drifts present after a storm." 

 These are sand-dunes, or dunes, as they are termed by Lyell, and their 

 surprising mobility, in the ever-changing direction and force of the 

 winds, is a subject of scientific and popular interest. 



Everywhere on the beach, in a dry, windy day, the sand-grains on 

 the surface are in motion. They are not carried through the air like 

 dust, except to a limited extent, when the winds are violent, but roll 

 or bound along the surface. Their motion, therefore, represents to 

 the eye, although less perfectly than snow or dust, the motions of the 

 invisible air. 



