G(.'i)li)(j]l i>f Richinoiid ('oHiifii. N. Y. 181 



land, is the gradual sinkiug of the coast. Prof. George II. Cook 

 has estimated the depression of the shores of N^ew Jersey and 

 Long Island at about two feet per century; others have thought 

 it somewhat less, but all are agreed that there is a subsidence 

 going on. It will be seen that if our coast settles down to ten 

 feet below its present level, the greater part of the plains extend- 

 ing south of the moraine from Giffords to Clifton, now the most 

 valuable farming land in the county, will be covered Avith salt 

 meadows within a few hundred years, provided that they are 

 not all washed away before by the action of the currents. 

 For a full discussion of this subject; sec Geology of New Jersey. 

 1868, pp. 343-3:4. 



EcoxoMic Geolouv. 



(1) Lro)i Ore. — The Linionite ore of Todt Hill, Four Corners, 

 and other places, has been used in blast furnaces in connection 

 with other more refractory ores, or has been screened, ground 

 and washed, to produce red ochre paint. The total amount 

 hitherto mined may be as great as 250,000 tons, and the present 

 production is about 20,000 tons per year. 



(2) Fire Clay. — The character of the dej^osits of this substance 

 has already been described. Messrs. Kreischer and Sons have a 

 large factory at Kreischerville, and produce refractory ware val- 

 ued at over 150,000 annually. Their supply of clay is jiartially 

 drawn from VVoodbridge, N. J. 



(3) Brick Clay. — Clays of glacial drift origin are used in the 

 manufacture of common brick near Richmond and Linoleumville. 

 The number of bricks annually produced has not been definite- 

 ly ascertained, but it probably amounts to several millions. 



(4) Trap Rock. — Quari'ies of this rock have been worked at 

 Graniteville and near Port Eichmond for many years. The rock 

 is either cut into blocks and shipped to New York to be used for 

 street pavements, or crushed into small pieces and employed in 

 Mac Adam or Telford pavements on Staten Island. Some edifices 

 have been constructed of this rock, but it is not well suited for 

 building purposes. 



