HURON COUNTY. 297 
When horizontal roots are well developed the tree is safely anchored, and 
is in no danger of being thrown out by the frost. So the stumps of dead 
trees remain undisturbed by the frost until the horizontal roots have 
rotted away. After that those having large top roots are rapidly lifted 
out of the soil by the action of the frost. I have repeatedly seen such 
swamps, with the remains of the horizontal roots two and three feet 
- above the surface, and others that had fallen down, having been com- 
pletely lifted out of the ground by the action of frost. In the elevation 
of these bowlders the frost may have had some influence, but it was 
probably slight. It is not necessary to assume that the trunks of the 
trees were here elevated by the growth of the roots, though it is proba- 
ble that they were. If we may assume the fact that the horizontal roots 
would pass under these bowlders, and maintain their normal growth . 
under the pressure, their slow and steady elevation would follow as a 
necessary result. 
Remains of other sand ridges ee that dscenti vad can be detected in 
other parts of the county. Between Norwalk and Olena, on the line 
which separates Bronson and Hartland townships, the surface presents 
to the eye the appearance of a broad, level plain of rich sandy loam, 
but it rises imperceptibly to the height of two hundred and fifteen feet 
above the sand ridge at Norwalk, or three hundred and sixty feet above 
the Lake. This’originally supported a dense forest of oak, hickory, black 
ash, elm, ete. About one mile east of Olena a long, sandy and gravelly 
ridge rises to the height of three hundred and ninety-five feet above the 
Lake. It has & nearly north and south direction, sloping on the west 
gradually to the general level of the plain, and descending abruptly to 
it on the east, the top being thirty-five feet above this general ‘level. 
- The materials here have been assorted by the waves and wind in the 
same way as those of the northern ridge. 
Near the north-east corner of Hartland township there are also the 
remains of another sand ridge, fifty feet lower than the last, which has 
suffered much from erosion, and is cut up by very irregular valleys lead- 
ing down to the west branch of Vermillion River, exposing the coarse 
Drift below, with many large striated bowlders. 
In the western part of Fitchville township a long, sandy ridge, trend- 
‘ing nearly north and south, rises in the highest parts to four hundred 
and twenty-five feet above the Lake, rising ten to fifteen feet above the 
level land to the east, and twenty to twenty-five feet above that on 
the west. The land to the north-west of this is a plain, diversified by 
irregular sand ridges and dunes descending gradually to a lower level, 
and marking the gradual descent of the waters of.the old lake. On these 
e 
