The principal streams of the county are Peekskill Creek, Furnace Brook, the Croton, Pocantico and Neperhan Rivers, and Tippett's Brook, tributary to the Hudson and the Bronx Rivers ; Westchester and Hutchinson's Creeks, Mamaroneck aud Byram Rivers, flowing into Long Island Sound ; Maharness and Stamford Mill Rivers, flowing east into Connecticut ; aud Muscoot Creek, Plumb Brook, and Titicus, Cross and Kisco Rivers, tributaries of the Croton. A number of small lakes are located chiefly in the more hilly districts in the north and west. The chief of those are Waccabuc, in Lewisboro; Cross Lake, in Poundridge; Byram Lake, in North Castle; Rye Pond, in Harrison ; and Croton and Mohegan Lakes, in Yorktown. The southeastern portion of the county along the Sound is deeply indented by bays and estuaries, which in some instances are bonlored by large marshes. By the reflux action of the tide in the streams flowing into the Sound, hydraulic power is furnished which is utilized in several places.

The geological formations of the county have al- 4'J

ready been described, but it may be added that to its other advantages as a place of residence Westchester adds the important one of an abundance of building stone of the best quality. There are valuable quarries of marble at Sing Sing and traces of valuable ores have been discovered. Several mineral springs have been found in dirterent portions of the county, chief among which is Chappaqua Springs, three miles east of Sing Sing, and esteemed for its medicinal qualities.