Topographically, it consists of two main ridges and an intermediate one, liaving their axes parallel with the Palisades of New Jersey, and a direction northnortheast. 1. Spuyten Duyvil Kidge, from Yonkers city line to Spuyten Duyvil Creek, and between the Hudson on the west and Tippett's Brook ' on the east. Greatest elevation, two hundred and eighty-two feet, ' ou land of Frederick Goodridge, Iliverdale. 2. Valentine's Ridge, from Yonkers line to West Farms line, and between the Bronx ^ on the east and Tippett's Brook on the west. Greatest elevation, two hundred and forty feet, near Woodlawn Heights. 8. Van Cortlandt Ridge, intermediate, from Y'onkers line to Vault Hill, between Tippett's Brook on the east and its main branch on the west. Greatest elevation, two hundred feet, near Yonkers city line.

Tippett's Brook, the main stream, rises in Yonkers, rtows southwesterly until it forms Van Cortlandt Lake,* below which it is a tidal stream to its outlet into Spuyten Duyvil Creek. About twenty lesser brooks, varying in length from five hundred to ten thousand feet, flow into the Hudson, the Bronx and Tippett's Brook.

The geological formations are very ancient, consisting mainly of micaceous gneiss or granite, * the former largely preponderating, the exposed surfaces indicatingsubjectionto intense heatand pressure, with so great displacement that the strata are nearly vertical, outcropping in numerous parallel ledges, not continuous, but cii echelon, and giving steep inclination to hillsides. A coarse, crystallized limestone" of varying hardness, ranging about north-northeast, crops out at King's Bridge and on the Whiting and Delafield estates, Spuyten Duyvil Ridge. On the latter ridge the surface of the primary rocks is strewn with trap boulders.