54 



EDWIN W. HUMPHREYS AND ALEXIS A. JULIEN 



crystalline rocks which have escaped the glacial scouring. It 

 therefore may be added that we find abundant evidence of the wide 

 distribution of tundra and peat-bogs all over this region, for a long 

 period before the advance of the continental glacier as well as since 

 its retreat. In the adjoining region, Westchester County, Mather 

 recorded, sixty years ago, observations on peat-bogs, covering in 

 the aggregate nearly 400 acres. Throughout the Bronx tract, in 

 all directions around the locality we have described, we have noted 

 many remnants of these, in street and house excavations, which 

 have not yet been destroyed by the advances of the great city. 



These now vary 

 widely in area and in 

 depth. A few in- 

 stances will be pre- 

 sented to show that 

 this form of chemical 

 corrosion must have 

 been here an active 

 factor in degrading 

 even the elevations 

 of the rock-surface. 



Thus, along the 

 low valley now oc- 

 cupied by Morris 

 Avenue, the depres- 

 sion in the glaciated surface was formerly filled with peat, even 

 now particularly well shown in the vicinity of 170th Street. In 

 filling in this street with rock, the peat was forced up in places to 

 a height of ten feet on each side, and its surface cracked in all direc- 

 tions, revealing pockets of fresh- water shells. Thence the bog 

 certainly stretched for a quarter of a mile, with a width of several 

 hundred feet; while there is evidence of its former extension south- 

 ward, probably as far as the Harlem River, and northward for an 

 indeterminate, but long, distance. At 178th Street and Honeywell 

 Avenue, a peat-bog yet remains and has recently been partially 

 excavated, of which the original area, we estimate, must have occu- 

 pied several hundred acres along the low valley. Its depth, as 



Fig. 8. — Another bowlder that was forced into a slab. 



