362 Geology of Long Island. 



This subsidence probably began in the later Quaternary and may 

 be still continuing. 



Economic Geology. 



Magnetite : this is the only metallic ore found on Long Island, 

 and occurs almost everywhere on the beaches in the form of sand. 

 It is not, however, sufficiently abundant in any one locality to 

 render its collection profitable. A company was started some 

 time since for the purpose of separating the ore, in the vicinity 

 of Quogue, from its associated quartz and garnet sand by means 

 of powerful electro-magnets, but the enterprise proved unsuc- 

 cessful. 



Iron Pyrites in its white variety, or marcasite, is common in 

 the lower clay-beds, but does not occur in sufficient abundance 

 to pay for utilizing it. 



Lignite occurs only in small quantities and usually at great 

 depths. 



Peat of an inferior kind, composed of the matted roots of 

 grasses and other plants, occurs at the heads of most of the bays 

 on the south shore, but is not used to any extent. 



Although not productive of any of the valuable minerals, Long- 

 Island may be considered peculiarly rich, from the fact that 

 almost the whole of the island can be utilized in the arts- and 

 trades. Its sands and gravels are of every kind in use, and ifs 

 clays are suited for the manufacture of fine grades of brick 

 and pottery. The former materials are largely shipped from 

 Port Washington and the vicinity, for building purposes. 



The most extensive deposit of fine pottery clay occurs at Glen 

 Cove, on the premises of the Messrs. Carpenter. This clay is 

 very plastic and burns a light cream-color. The friable quartz 

 pebbles described above, produce when ground the finest quality 

 of white sand for glass and pottery. The deposit of kaolin is 

 also unsurpassed. In addition to these materials, this locality 

 furnishes fire-sand for pottery, grey and blue pottery clays, and 

 an excellent fire-clay. 



The next locality of note is Huntington. In this town is an 

 immense deposit of the finest brick-clay, upheaved to such an 

 elevation that it is easily accessible. The beds are worked at 



