CARBONIFEROUS. 369 



iferous would be east of such a line, while at other places the Cretaceous 

 would be west of it. At the point where the Brazos River crosses that line 

 it has cut down into the strata until the Carboniferous can be traced in the 

 valley of the river as far southeastward as the line of Hood County. Again 

 there is an extension of the Cretaceous strata forming a high ridge, between 

 near Carbon and the southwest corner of Comanche County, extending to the 

 westward almost to the Permian border at Elmsdale; and then again the Car- 

 boniferous is found along the Lampasas River from its source to the town of 

 Lampasas. This strip of Carboniferous is confined entirely to the valley of 

 the river. Again there is a small strip of Carboniferous near Marble Falls, 

 and in Honey Creek Cove in Llano County. 



Along the southern line the Cretaceous comes down on the north almost 

 to the west line of San Saba County and extends along parallel with that line 

 and finally crosses it near the head of Brady Creek. The Brady Mountains 

 are Cretaceous and are cut through by erosion, showing the Carboniferous 

 only in one place, at Cow Gap, on the road between Brady City and Coleman. 



The following is a list of the counties which are in whole or in part Car- 

 boniferous: Montague, Wise, Jack, Parker, Palo Pinto, Young, Throckmor- 

 ton, Stephens, Eastland, Erath, Callahan, Coleman, Brown, San Saba, Lam- 

 pasas, McCulloch, Concho, Runnels, Taylor, and Shackelford. 



The Carboniferous formation in Texas belongs to the Western Interior 

 Coal Producing Field, composed of Missouri and the States adjoining on the 

 north, west, and south, and reaching through, with some interruptions, into 

 Texas. (Dana's Manual of Geology, p. 309.) 



It is directly connected with the Carboniferous beds of the Indian Territory. 



The area in Texas is subdivided into two fields by the overling Cretaceous 

 rocks which extend entirely across the formation just south of the Texas and 

 Pacific Railway. We have called the northern division of these beds the 

 " Northern or Brazos Coal Field," and those on the south the " Central or 

 Colorado Coal Field." 



The upper strata of the two fields are the same, but there is a great lapse 

 of time between the lower sandstones in the Central Coal Field and the lime- 

 stone immediately below them, as seen at the junction of these two beds in 

 the vicinity of Lynch Creek and elsewhere along the line of contact between 

 the two. The thickness of the formation in Northern Texas is about three 

 thousand seven hundred and forty feet, by actual measurement on a line run 

 from the upper part of the measures at the northeast corner of Throckmorton 

 County, to the west line of Hood County. 



The thickness of the beds in the Central Coal Field is about six thousand 

 and nineteen feet, on a line run from the head of Pecan Bayou to the town 

 of San Saba. Detailed sections along these lines are given beyond. 



