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ject to explanation. LEvery locality has had its history, extending 
through aeons of geological time. If we wish to explain the pres- 
ence of the boulders in the Botanic Garden we are brought face 
ogical history of the Botanic 
_— 
to face with the problem of the geo 
Garden site. 
What Is an Explanation? 
The first step toward explaining a thing is to describe it ac- 
curately. In fact, scientific explanation consists largely (some 
scientists say wholly) in extended, detailed, and accurate descrip- 
tion. We shall, therefore, describe the boulders and also the 
geological and topographic features of the Botanic Garden as the 
first and necessary step in unravelling the mystery of the origin 
of these boulders. 
The “ Back Bone” of Long Island 
One who walks through the Garden will notice at once that the 
land in the northern portion is considerably higher than in the 
southern part. Just west of the Laboratory Building is a con- 
siderable hill with a large boulder resting on the surface at the top, 
and known, from this feature, as Boulder Hill. 
If one travels eastward on Long Island, or (more conveniently ) 
studies a topographic map of the Island, he will see that this high 
land extends as a conspicuous ridge from Fort Hamilton, on the 
west, through Prospect Park and the Botanic Garden to Montauk 
Point, at the eastern extremity of the Island. This ridge, some- 
times referred to as the “ back bone” of Long Island, lies (in the 
western part) considerably nearer the north shore than the south 
shore. At and near the eastern end of the Island the ridge has 
been worn away by the action of ocean waves and this explains the 
cliffs near Montauk. But, wherever the ridge has been worn away 
by the waves, or exposed by excavation, it is found to be com- 
posed of sand and gravel in which are imbedded big boulders. 
A similar ridge may be traced all the way from southern Rhode 
Island across [isher’s Islands and Plum Island to Orient Point, 
and thence along or close to the northern shore of Long Island to 
about the vicinity of Manhasset, where it joins the other ridge. 
