No. 101.] 
Economical Uses of Sands. 
Three kinds of sand are found on Long Island, viz: siliceous 
sand, garnet sand and iron sand. These sands are mixed with each 
other in variable proportions. They result, as has before been re- 
marked, from the degradation of land, the disintegration of bould- 
ers, and the grinding up of pebbles by the action of the surf. 
The siliceous sand is found every where along the coast, and 
constitutes most of the soil of the island. In some localities, it 
contains grains of red and yellow feldspar; in others, grains of 
black hornblende. Much of it is of good quality for the manufac- 
ture of common glass, for sawing marble, and for making mortar. 
Red garnet sand is not uncommon on the shore.* In some ope- 
rations, this sand may perhaps be used as a substitute for emery. 
Magnetic iron sand is found in small quantities along the whole 
coast of Long Island, where the surf beats on the shore. It is so 
abundant in some localities after storms, that perhaps it may be col- 
lected for blotting sand and for iron ore. Layers of it two or 
three inches thick were seen in many places. 
Garnet and iron sands both occur more abundantly after storms; 
and the reason is, that the surf, as it rolls upon the beach, carries 
the various kinds of sand along with it, and during the reflux of the 
wave, the water washes back the lighter grains, leaving the heavy 
sands behind. Each wave repeats this process, and the garnet 
and iron sands thus accumulate in layers. The same principle is 
applied in the artificial separation of metals and ores from sand 
and pulverized rocks in metallurgic operations. 
Salt MarsheSf or Marsh Alluvions. 
Salt marshes are very extensive on the coast of Long Island, 
and they are of much value for meadow lands. These alluvions 
result from a combination of several causes. The first step in 
their formation, is, the deposite of a sand or shingle beach, by 
marine currents sweeping along detrital matter, and depositing it in 
the eddy currents, in front of shallow bays and re-enterings of the 
coast, so as to shelter these spaces from the action of the surf, if 
they were before exposed to it. They are also made shallower 
* The most interesting localities are at Oyster Pond point, the shore between Old Man*i 
and Miller's place, and that between Horton's point and Mattituck inlet. 
