Yonkers, Hastings-on-the- Hudson, Dobbs Ferry, Abbotsford, Irvington, Tarrytown, Sing Sing, Croton, Crugers, Verplanck and Peekskill, are the principal stations along the line of this road.

The New York and Harlem River Railroad extends through the central portion of the county, through Morrisania, West Farms, Eastchester, Scarsdale, White Plains, Mount Pleasant, New Castle, Bedford, Lewisboro and North Salem. Mount Vernon, White Plains, Pleasantville, Mt. Kisco, Katonah, and Croton Falls, are the principal villages along its line. At William's Bridge, the New York and New Haven Railroad branches and runs through Eastchester, Pelham, New Rochelle, Mamaroneck, Harrison and Rye.

The New York City and Northern Railroad enters the county in Kingsbridge, and diverging there from the Hudson River Road, passes through Van Cortlandt. South Yonkers, and North Yonkers, up the Neperan Valley through Odells, Ashford, Elmsford or Hall's Corners, and leaves the valley at East Tarrytown ; thence by Tarrytown, North Tarrytown, Tarrytown Heights, Whitson, Merritt's Corners, Croton Lake South, Croton Lake North, Yorktown, Amavvalk. West Somers, Baldwin Place, Lake Mahopac, Carmel, Tilly Foster's, and terminates at Brewster, where connection is made, via Danbury, with the New England system.

Geology.' -- The rocks which compose New York Island, and underlie the adjacent country on the north and east, are chiefly gneiss and mica-schist, with heavy, intercalated beds of coarse-grained, dolomitic marble and thinner layers of serpentine.' These are all distinctly stratified, and, according to Prof. Dana, have once been sedimentary beds deposit-

1 The accompanying geological map of Westchester County was prepared by the officers of the United States Geological Survey, at Washington, D. C, from data prepared by Professor Dana, and presents the latest conclusions of that school of geologists who agree with Prof. Dana as to the Lower Silurian age of the Westchester County rocks. The geological portion ol' this cliapter was written at the office of the Geological Survey, at Washington, and eubniitted to Prof.