250 
Transactions Texas Academy of Science. 
Tare, Ealph S. 
glacial regions, as I understand those conditions. I refer to the valley 
of the Colorado in Central Texas. 
“The river is here superimposed upon a hard Silurian barrier which is 
effectually retarding its downcutting, although the river is still well above 
ibase level. One of the effects of this retardation of development on the 
region upstream from the barrier is that a temporary base level is pro- 
duced, and the Colorado itself and the side streams are, for a certain 
distance, actually building up their beds. The effect of the barrier is thus 
felt for forty or fifty miles; but above this, the flow is rapid and the river 
is degrading its channel. Along the entire course the side streams are 
rapidly at work, and from these two sources much sediment is being fur- 
nished. Owing to the many soft beds of Cretaceous. Permian and Carbon- 
iferous through which these streams are flowing, the amount of sediment 
supply is very great. 
“Another point of importance in this connection is the peculiarity of 
rainfall. The immediate region is sub-humid, the extreme headwaters are 
in a truly arid region. Consequently, the water supply, during fhe greater 
part of the year, is small in amount; but heavy rains, which are of annual 
occurrence, and often of greater frequency, bring to the river vast floods 
of water, which the ordinary channel is totally unable to hold. Almost 
the entire rainfall has to be carried off, for the barren soil holds but little, 
and the violence of the rain speedily forms it into rills and rivulets even 
where no drainage lines previously existed. While this is written chiefly 
with reference to the arid headwaters it applies almost equally to all the 
streams, even those of the sub-humid belt. These tributaries, during the 
greater part of the year, consist of a few pools, often isolated, sometimes 
connected by a slowly trickling stream. These pools are enclosed com- 
monly in bars or delta bars in the stream channel, formed during flood 
times, and the violence of these floods is attested by the presence of drift 
wood lodged in the pecan trees many feet above the low water stage of 
the stream- In the Colorado these are sometimes at an elevation of fifty 
feet above the low water surface.” 
A parallel is now drawn between the conditions here recorded and those 
existing at the time of the formation of the terrace deposits at the close 
of the Glacial period. 
400. 
ISTotes on the Physical Geography of Texas. 
Proceedings of the Acad, of hfat. Sciences, Pt. II, pp. 31e3-347. 
Phila., Apr.-Sept., 1893. 
Contents: Preface. Parti. General Description. 1. General Geogra- 
phy. (a) Topography, (b) Drainage. 2. General Cliniatic Conditions. 
3. General (Geologic and Geographic Development, (a) Pre-Oarbonifer- 
ous Land. (b) Carboniferous modiflcation of the older Paleozoic 
Land, (c) Jura-Trias Period of Denudation. (d) Cretaceous Subsi- 
dence. (e) Post-Cretaceous Changes. (f) Post-Cretaceous Drainage. 
Part II. Physiographic Description. 1. General. 2. The Quaternary 
(bastal Prairies, (a) Geographic Description, (b) Young, Oonsequent, 
