IOWA ACADEMY OP SCIENCES. 
65 
with a crude admixture of sand, mud and fragmentary vege- 
table detritus which, as said, becomes at length indistinguish- 
able from the overlying drift. 
In the very lowest portion of the (upper) drift, and often 
resting directly on the peat seam proper, are quantities of half- 
decomposed wood, not rotten wood at all, rather wood which 
has lost 'its lignin and of which only the cellulose basis remains, 
but showing ail the original structure elements and features 
with perfection absolute. The wood seems identical with that 
of Larix americana Mx. 
The facts before us would seem to warrant the following 
conclusions in reference to the state of affairs or conditions 
under which the peat bed was laid down: The Hypnum fluitans^ 
free from all foreign matter of every kind, bespeaks a wide, 
clear, open marsh or peat- bog to which anything like muddy 
drainage from the surrounding regions never came. Here for 
a long period, probably centuries, the moss must have flour- 
ished undisturbed, but was at length completely submerged and 
drowned, probably by the closing of the drainage outlets. In 
the deeper water that succeeded flourished a difl!erent flora, 
probably a surface aquatic flora such as the Lemnas, filamentous 
algae, Anacharis, possibly, whose dying fronds and filaments 
settled through other centuries to form at last the second layer 
of our peat bed seam. Over this, as has been stated, lies a 
mixture of organic and inorganic matter. Whether this was 
deposited in situ by another change in the depth of the water 
and local surface conditions or whether this represents the low- 
est part of the drift sheet as it came is difficult to say. In this 
particular layer there are evidences not a few of the presence 
of higher plants, monocotyledons chiefly. These may have 
been pushed in from other shallower parts of the same marsh. 
However this may be, the final catastrophe is not a matter of 
doubt. The whole region was slowly frozen up and at length 
whelmed by an icy deluge of frozen mud, fragments of swamp - 
loving trees wrenched and broken as they came, sand boulders, 
detritus of all the surrounding surface soils, whatever their 
variety, their flora or formation. Once this process complete, 
our peat bed remained hermetically sealed, unaffected, doubt- 
less, by subsequent surface changes of any sort until stirred 
by the plowshare of the railway engineer. Considering the 
assumed great age of the deposit the state of preservation in 
which the plant remains occur is truly noteworthy. But then 
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