482 



SCIENCE. 



[N. S. Vol. IX. No, 222. 



alone there are no fewer than five, and two of 

 these — the Travis Peak, or Waco, and the Ed- 

 wards — receive consideration in this paper." 



To those familiar with the Texas Cretaceous 

 a change in nomenclature is at once noticeable 

 — the term ' Travis Peak ' being emploj'ed for 

 the formation heretofore known as ' Trinity 

 Sands,' and 'Edwards' for the ' Caprina lime- 

 stone.' These and similar changes are made, 

 as the authors state, by refining the previous 

 nomenclature, appropriate geographic names 

 being substituted wherever possible for paleon- 

 tologic and mineralogic terms. 



An investigation of the source of the artesian 

 water at and in the vicinity of San Antonio was 

 productive of the following results: "That 

 while these well waters come from the same 

 series of beds that supply the artesian wells of 

 the Waco, Fort Worth and Dallas region north 

 of the Colorado, their occurrence prese'nts some 

 important differences of detail. Instead of 

 having their immediate source in beds of porous 

 sands, like the wells about Waco, they are de- 

 rived largely from the Edwards limestone, 

 hitherto supposed to be one of the most imper- 

 vious formations of the whole Cretaceous sec- 

 tion " (p. 200). " It became apparent," the re- 

 port continues, ' ' that this hitherto unappreciated 

 water-bearing formation had great possibilities 

 for supplying with flowing or non- flowing wells 

 a large area of country lying between Austin 

 and San Antonio, extending west of the San 

 Antonia River along the northern margin of the 

 Rio Grande Plain towards the Pecos River, and 

 even comprising the extensive summit region 

 of the Edwards Plateau" (p. 200). 



Two classes of outflowing waters are recog- 

 nized — the one following the margin of the Rio 

 Grande Plain, the other appearing in the can- 

 yons of the Edwards Plateau. 



The introduction which has here been briefly 

 outlined gives but a faint idea of the detailed 

 work which has been so creditably done by the 

 authors. 



The geography of the region is now taken up, 

 the chief features of which are the Rio Grande 

 Plain, the Edwards Plateau and its _ 'jagged 

 southeastward front ' called the Balcones Scarp. 

 " Broadly considered, they are a lowland plain 

 inclining gentlv southeastward to the Gulf of 



Mexico, an upland plain rising gradually to- 

 wards the northwest, and a rugged zone of 

 separation which includes a quick ascent from 

 plain to plain." 



The Rio Grande Plain is characterized by a 

 low relief, yet attention is called to the fact that 

 occasionally hills of considerable magnitude are 

 encountered ; buttes, capped with limestone, or 

 sedimentary below and igneous above ; old vol- 

 canic necks, as Pilot Knob, south of Austin ; 

 rounded masses of basalt, as Sulphur Peak, in 

 Uvalde county. ' ' The Anacacho Hills, extend- 

 ing east and west in southern Kinney countj'" 

 and constituting the most rugose part of the 

 plain are of still another type, consisting of a 

 monocliual plateau, or cuesta, sloping south- 

 ward and presenting a steep scarp to the north." 



Climatically the plain may be divided into 

 the eastern, or humid and sub-humid region and 

 the western, or arid region. Beyond Bexar 

 county continuous cultivation is impossible on 

 account of aridity. 



The Balcones Scarp, the position of which 

 " is determined by a complex dislocation of the 

 rocks, the Balcones fault," is the dissected edge 

 of the Edwards Plateau. Numerous hills of 

 denudation, locally known as mountains, here 

 rise above the Rio Grande Plain — in the vicinity 

 of Austin, 400 feet ; in Uvalde county, 1000 feet. 



The elevated Edwards Plateau merges into 

 the Llano Estacado. Between them there is no 

 definite line of separation, yet their surface 

 characters, soil and rocks, give to each a pecu- 

 liarity of its own. 



The main drainage of the Edwards Plateau 

 is to the east and southeast, and, as its water- 

 shed lies well to the westward, the erosion of 

 the streams flowing into the Pecos is but 

 moderate. 



The observer iu crossing the Balcones line 

 " experiences a sudden and complete change of 

 scenery, with accompanying changes in floral, 

 geologic and cultured conditions." Three sim- 

 ple topographic elements are presented, viz.: 

 "The flat-topped summits of the decaying 

 plateau ; the breaks or slopes of its crenulated 

 borders and canyoned valleys ; [and] the stream 

 ways." 



The cap-rock of the plateau is the Edwards 

 (Caprina) limestone. 



