181 
the latter, The upper surface of the underlying rock is not 
smooth (Ifig. 13). 
In a region known to have been occupied by glacial ice the soil 
deposited directly by and mostly under the ice forms an uneven 
blanket with hummocks and ridges consisting of a largely un- 
assorted mixture of all sorts of material from fine clay to large 
boulders. This material is called till. Where the ice border ad- 
vanced or remained stationary for some time it pushed together 
and built up irregular ridges of loose material, called moraines. 
The ridge on which the Brooklyn Botanic Garden is situated has 
all the characteristics of a moraine. Gravel, sand, silt, and clay 
washed out from the ice-border on land, in lakes, or in the sea 
formed other characteristic deposits. 
Hypothesis, Theory, and Fact 
To make a long story short, it may be said that the hypothesis 
of a glacial period for a large portion of the North American con- 
tinent (including Long Island and the site of the Brooklyn Botanic 
Garden) has been thoroughly tested and verified to such an extent 
that the hypothesis became first a theory (i.e., a largely verified 
hypothesis), and finally the idea passed from the realm of hy- 
pothesis and theory, and is now considered as corresponding to 
actual fact. The influence of Agassiz won the support of others, 
including the great geologist, Lyell, but the glacial theory was not 
universally accepted until about sixty years ago. 
A Glacier on Long Island 
, 
The “ back bone’ 
and hilly northern portion of the Botanic Garden, is a moraine. 
of Long Island, which includes the higher 
This fact seems first to have been clearly stated by Elias Lewis, Jr., 
in a letter to Prof. James D. Dana, of Yale College. This letter 
is published in the American Journal of Science and Arts, Volume 
XIII (3d Series), 1877, page 235. The boulders have been trans- 
ported by ice from Manhattan Island, New Jersey, southern New 
York State, and New England, and occasionally all the way from 
the Adirondacks. In transit they have been rounded, smoothed, 
and scratched. 
