PHYSICAL ASPECT OF THE GROUNDS. 



The extreme length of the Park from north to south is 

 4,950 feet, or 330 feet less than one mile; and its extreme 

 width is 3,120 feet, or three-fifths of a mile. Roughly es- 

 timated, one-third of the land area is covered by heavy 

 forest, one-third by open forest., and the remaining third con- 

 sists of open meadows and glades. The highest point of 

 land in the Park is the crest of Rocking Stone Hill, the 

 elevation of which is is 94.8 feet above sea level. 



Topography. — Speaking broadly, the Zoological Park is 

 composed of granite ridges running from north to south. 

 In many places their crests have been denuded of earth by 

 the great glacier which once pushed its edge as far south as 

 New York City. In the valleys lying between these glacier- 

 scraped ridges, great quantities of sandy, micaceous soil 

 have been deposited ; but in one spot — the Wild-FoAvl Pond 

 — what was once a green, glacial lake fifteen feet deep, pres- 

 ently became a vast rock-walled silo filled with vegetable 

 matter and a trembling bog of peat. Everywhere in the Park 

 glacial bowlders of rough granite or smoothly rounded trap- 

 rock, varying in size from a cobble-stone to the thirty-ton 

 Rocking Stone, have been dropped just where the warm 

 southern sun freed them from the ice. The Park contains 

 thousands of them, many of which have been removed from 

 walks and building sites only with great labor. 



In three of the four principal valleys of the Park, bogs 

 have been converted into ponds, and in the largest and deep- 

 est of all lie Bronx Lake and Lake Agassiz. Tha bed-rock 

 underlying or cropping out in the Park exhibits pink gran- 

 ite, gray granite, rotten gneiss, and quartz in bewildering 

 variety. Occasionally in trench-digging a ledge is encount- 

 ered which yields good building-stone for rough work, but 

 usually our rock is so full of mica as to be worthless. 



The water-levels in the various portions of the Park are 

 as follows 



Above Sea Level. 



Surface of Bronx Lake 20.40 feet 



Surface of Lake Agassiz 31.70 " 



Surface of Cope Lake and Duck Ponds . . 47.00 ' ' 



Surface of Wild-Fowl Pond 6.5.00 " 



Surface of Beaver Pond 44.00 " 



9 



