42 Soils of Nebraska — Hicks. 
the Tertiary include nearly all the kinds previously mentioned. 
Limestone of the ordinary kind, rotten limestone, ordinary 
sandstone and calcareous sandstone, indurated clays and soft 
clays, conglomerate, lignite, and quarfczite, are all found in the 
Tertiary. Loose sands also occur in great abundance, and as 
they are driven to and fro by the wind form the belts of "sand 
hills" which mar the beauty and productiveness of many town- 
ships. Marl of fine quantity for fertilizing, and thick beds of 
peat, are also found in the Tertiary. 
The so-called "bad lands," or mauvaises terres^ of the Tertiary 
are formed by erosion in the indurated clays and marls which 
yield to running water readily enough to form deep gullies in 
the line of the current, and yet have the requisite firmness and 
tenacity to stand up in steep walls against the weather. These 
bad lands constitute a temporary stage of the evolution of sta- 
ble laud surfaces in soft strata. So long as the little streamlets 
have a rapid fall they gouge out deep gullies with steep walls. 
Each side channel entering the little valley forms a tributary 
canon, which again forms its tributaries, until an intricate 
maze of principal and tributary canons is produced. In the 
process of formation while erosion is in rapid progress no vege- 
tation can obtain a permanent hold in any of the gullies. But 
as the system enlarges and the tributary canons run into each 
other, the central stem of the tree-like system widens out and 
ceases to become deeper because the natural drainage level has 
been reached. Grasses, weeds, shrubs, and trees take root. 
The steep walls are washed down to gentle slopes which pres- 
ently take on the grateful green of the valley. Thus the whole 
region which the water had cut into barren, forbidding, and 
impassable gullies, may be transformed into fertile valleys. The 
process is too slow, however, to make it advisable to locate 
claims in the bad lands. Like all geological processes, it re- 
quires ages to work these changes. The whole continent is 
gradually approximating a condition of stability as regards 
erosion but that condition will not be reached until the whole 
surface is reduced much nearer to the level of the sea than it is 
at present. 
The bad lands and sand hills, however, form but a small part 
of the country occupied by the Tertiary. Some of the best 
grazing and arable land in Nebraska may be found in the bed 
