76 BIG SPRING PRAIRIE. 
WOODS ON CLAY BANKS AND CLAY ISLANDS. 
These two divisions may be considered together, 
as the same factors of shallow muck and a clay subsoil 
are common to both. By even a slight drainage the 
water will move down the clay incline, giving the 
proper condition for the development of thickets fol- 
lowed by forests upon it. Mr. Peter Brayton stated 
that a thicket originated in the vicinity of new road 
No. 2 after the first ditch was dug. The clay subsoil 
continues the slope of the adjoining ridge. In conse- 
quence, there was developed a thicket extending from 
a point southwest of the Big Spring in a westerly and 
southwesterly direction. In 1895 it was far more ex- 
tensive than is figured on Map J, for by 1899, many 
acres had been cleared and brought under cultivation. 
One of the first trees to make its appearance upon 
these areas is Populus deltoides (Cottonwood), suc- 
ceeded by Ulmus (Elm), Acer (Maple), and Fraxinus 
(Ash). The trees in woods just south of new road 
No. 2 were from 10 to 15 inches in diameter. 
Fig. 16 represents Clay Island of Map II. This area 
in 1899 contained four elms over 3 feet in diameter, and 
two over 2 feet in diameter, besides a few smaller ones. 
There were also about 50 small ash trees, some of which 
originated from the stumps of former larger trees, as 
sometimes from four to six of these trees are grown 
together at the base. All of these trees exhibited the 
characteristic prominent roots. Some of the clay 
islands were wooded before the first ditches were dug. 
The effect of ditching was to cause a more rapid en- 
croachment of forest upon the surrounding portions 
which were underlain by a properly sloping clay- 
subsoil. By 1886, the forest had encroached consider- 
ably upon the prairie to the southwest, south and south- 
east of it where the proper natural slope of clay subsoil 
occurred. In this year a severe prairie fire destroyed 
