180 a eiAogy of Richmond Couni 11^ J\'. Y. 



grasses and ruslies, while true peat results from the growth and 

 decomposition of mosses. 



Encroavli.ment of the Lower Bay. — The entire southeastern 

 shore of Staten Island is gradually being Avashed away, and 

 hence receding to the westward. In some places the loss is very- 

 apparent'. At the foot of New Dorj) Lane, near where tlie Elm 

 Tree Lighthouse is now situated, a large American elm was 

 standing not longer ago than the year 1840. The place where 

 this tree grew is now beyond the end of a dock which extends 

 some four hundred feet from the shore. This indicates a loss 

 of four hundred feet in forty years, or an average of ten feet per 

 year. At Cedar Grove, half a mile south of this i^oint, there 

 has been a loss of about three hundred and tliirty feet since 

 1850, or about the same average. At Prince's Bay, the Govern- 

 ment has been obliged to build a heavy sea-wall in front of the 

 bluff on which the lighthouse is placed, — and a like precaution 

 has been taken at the forts on the Narrows. 



Now there are two causes operating to effect these results ; 

 they are (I) the constant abrading action of the waves and cur- 

 rents, and ("2) the gradual dejiression of the coasts. From the 

 course of tlie currents in the Lower Bay, the. eroded material, 

 together with pai't of that brought down by the I'ivers, is carried 

 southwardly along this coast, the sands deposited as beaches, 

 bars and points, while tlie finer muddy part is carried farther, 

 and finally deposited in the deeper waters of the Bay or in the 

 ocean. 



It has been the custom to save property from this very serious 

 loss by building bulkheads filled with stone, some hundreds of 

 feet outward from the shore at the southern end of the land 

 to be protected. These bulkheads aCt to break the force of the 

 sand-bearing current flowing along the shore; and this check to 

 to the motion of the water, causes it to deposit its burden on the 

 north side of the dock. The waves soon drive the sand up on 

 shore, and land is actually made in this manner. It is probably 

 the cheapest and most effective way of protecting property on 

 this coast. 



The second cause which is in operation, and which, although 

 very much slower, is perhaps surer to submerge much valuable 



