135 
In the morning of August 4 we moved camp again, following the post- 
road to a point about a mile south of Abby post-office. Here was a 
big wet valley, containing four ranches. 
August 7 we set out for the head waters of the south fork of Dismal 
River, and at noon stopped near Swan Lake, collecting there for a few 
hours. Late in the evening we arrived at West Cody Lake, situated 
on a cattle range once occupied by Mr. W. I. Cody, better known as 
* Buffalo Bill.” The Cody lakes are the head waters of South Dismal 
River, although the water runs beneath the surface of the sand for 2 
or 3 miles before it forms a visible stream. The region around the 
lakes was a good collecting ground. 
August 11 we moved our camp farther down the river to a place 
about 4 or Oo miles above the forks. August 15 we crossed the sand 
hills again to Mullen, when we drove down the Middle Loup Valley to 
Thedford. August 21 to25 we made a collecting trip to Plummer Ford 
to get the fall flora of Dismal River. 
Twas absent from official duty from August 26 to September 6, but 
beginning work again I confined myself to the region along the Bur- 
lington and Missouri River Railroad, collecting around Thedford Sep- 
tember 7 to 10 and 12 and 15, Halsey and Natick September 11, Mullen 
September 14, 15, and 18, Seneca September 16,and Whitman Septem- 
ber 19 and 20. 
FORMATION OF THE SAND-HILL REGION, 
Even if the sand-hill region was at some earlier period a lake forma- 
tion, it has, nevertheless, received its present form from the action of 
the wind—in fact it is still in the process of formation. The sand hills 
change their configuration constantly. Whenever the sand is not held 
together by the roots of plauts or by moisture, or is not otherwise pro- 
tected, it is little by little carried away by the wind. If a spot ona 
dry lull becomes bare the loose sand is blown away, a small hollow is 
made, the surrounding erass dies from drought, the dry sand, no longer 
held together by the roots, slides down into the hollow and in its turn 
is borne away, and thus the hollow becomes gradually larger and larger. 
Such “blowouts” were seen 100 meters in diameter and 15 to 20 meters 
deep. It sometimes happens that settlers a few years after breaking 
their land find a field transformed into a big blowout. The sand ear- 
ried away by the wind is deposited in great drifts, by which new sand 
hills are formed or the old ones inereased in height. There would be 
no stability whatever were it not for certain grasses that seem to thrive 
best just in these blowouts. When well established their roots bind 
the sand together and their decaying parts enrich the soil. Thus they 
give protection to the sand hills and render them suitable for other 
vegetation. Such blowout grasses are: Calamovilfa longifolia, Red- 
fieldia fiecuosa, Eragrostis tenuis, Muhklenbergia pungens. 
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