170 
thus, by the motion of the earth, been forced against their west 
banks and have consequently eroded or under-cut them more than 
the east banks. Careful studies made since this hypothesis was 
first proposed have raised grave doubts as to whether the facts 
really justify the conclusion, and the suggestion must be taken, 
not as demonstrated fact, but merely as an interesting hypothesis, 
to be tested by further study. 
A Prairie on Long Island 
A portion of the Long Island Plain, comprising about 50 square 
miles in the center of Nassau County, and about midway between 
the north and south shores of the Island, is known as the 
“ Trempstead Plains.” In a report on the field operations of the 
U.S. Bureau of Soils for 1903, J. A. Bonsteel referred to this area 
as being “a natural prairie east of the Allegheny Mountains. — It 
was treeless when first discovered and was originally used as com- 
mons for the pasturage of cattle and horses belonging to indi- 
viduals and communities.” As Dr. Roland M. Harper has noted, 
“there is not another place exactly like it in the world.” 
Over an area of several thousand acres the flora is almost ex- 
clusively of native plants, and this is one of the evidences that it 
has never been artificially deforested and has never been under 
the plow, for after a virgin area in the eastern United States is 
plowed leuropean weeds come in and tend to crowd out the native 
lora. 
“The natural vegetation,’ 
two habitat groups: that of uplands and that along watercourses. 
? iz 
says Tlarper, “may be divided into 
There 1s also a characteristic weed vegetation along roads 
and in abandoned fields. . . 2 The upland vegetation is by far the 
most extensive but that of the valleys is (or was) a little richer in 
” 
species.” 
If one excavates in the coastal plain or frontal apron above re- 
ferred to, he will find pebbles, gravel, and sand (that could have 
here and there layers of 
aa 
been moved by streams of water), anc 
clay. In digging the channel for the Botanic Garden brook large 
1c outlet of 
boulders were 
the Lake and extending to a point just down stream from the 
Hills Boulder Bridge. South of that point fewer large boulders 
-e continually uncovered, beginning at t 
