1879.] Texas in its Geognostic and Agricultural Aspect. 379 
Such a wholly continuous area, more than one hundred and twenty 
miles wide, and over two hundred miles long, lies in the northern 
part of the Hill-country of Texas. It forms a long rectangle, of 
which Dallas county is nearly the center, and this is the reason 
why this division, and especially the city of Dallas, have so rap- 
idly grown in importance, and this proves at the same time with 
what keen foresight railroad minats have stretched their iron 
roads through this section. 
This division is, however, penetrated in its north-western part 
by the so-called Cross Timbers, two strips of forests from eight 
to ten miles wide, the soil of which consists of the tertiary - 
_ elements, but their intermixture through the physical influences 
of the glacial period, since the extent was not very great, became 
much superior to that in Eastern Texas. Besides, it constitutes 
only a very small part of the division under consideration, and 
supplies at the same time, to the adjacent prairies, convenient and 
adequate material for fencing and fuel, which only in few places 
has to be procured from considerable distances. 
In the southern and south-western portion of the Hill-country, - 
as fat as the Rio Grande, the soil is also composed of sand, clay 
and lime, yet, as in the northern part, it is more frequently inter- 
rupted by tertiary clay and sand, but much more, and more 
injuriously to agriculture, is the ground filled with hard, reddish 
flint stones, from the size of a pigeon-egg to that of the fist. 
These originate in the Highlands north of it, on one side of the 
primitive mountains arising there, and still more from the exten- 
Sive chalk hills. This chalk formation of the Highlands is of a 
sandy character, hard, and enclosing a great number of sand and 
flint concretions. After the drift period they remained scattered in 
every direction, and this readily explains why these concretions 
are found not only in river beds but also on those higher localities 
surrounding the valleys, and particularly on hills. The soil of 
this part of the Hill-country is here and there so filled with these 
Stones that it is useless to undertake a thorough culture of it. 
Although these places, often interrupt the fertile soil, yet the lat- 
ter comprises a considerable area, and it is especially the river- 
bottoms which in the southern part of the Hill-country possess 
an immense productive power. In the valley of the San Antonio 
river, almost the entire bottom of the valley can be irrigated for — 
ue a great distance, yet this system of irrigation, constructed by the 
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