SOUTHERN PACIFIC LINES 9] 
lite that crops out in ridges northwest of Haymond, here about 300 
feet thick, lies on the northeast end of a great anticlinorium (an anti- 
clinal arch with subordinate flexures) which brings pre-Pennsylvanian 
rocks to the surface over a wide area in the central part of the Mara- 
thon Basin. The strata of the anticlinorium are folded into several 
sharp anticlines and synclines and are broken by overthrust faults. 
Owing to its great hardness the novaculite is a ridge maker, and its 
white outcrops are very conspicuous. 
Between the north end of these novaculite hills and Marathon the 
ilroad crosses a flat gravel-covered plain. To the south are low 
hills of the novaculite, and to the north less conspicuous hills of 
Dimple limestone. 
Marathon is a village of considerable importance, named for a 
general of the United States Army who established a road from Fort 
Stockton to Presidio in 1854. It is a local center for 
Marathon, large cattle interests and is the shipping point for the 
eget feet. quicksilver produced at the mines of Terlingua, 70 
New Orleans 9851miles. Miles to the southwest. These mines have been an 
important source of mercury since 1894 and produce 
2,500 to 3,000 flasks (of 76 pounds) a year (Bureau of Mines). At 
one time a rubber factory was operated successfully at Marathon, 
making use of the guayule plant (Parthenium argentatum) as long as 
the local supply was available. Resin from the candillia plant has 
also been shipped from Marathon for use in making phonograph disks. 
The village of Marathon is built on ledges of flaggy limestone and 
massive conglomerate of the Marathon limestone (Ordovician). 
This is the.only pre-Devonian formation well exposed near the rail- 
road, but in low hills not far south of Marathon there are extensive 
outcrops of strata from Cambrian to Devonian in age. West of 
Marathon low rugged ridges of Caballos novaculite may be seen to 
the south and behind them a high conical mountain of intrusive 
syenite, Santiago Peak, 25 miles distant (elevation 6,521 feet). To 
the west are the eastward-facing escarpments of the Del Norte 
Mountains, made up of limestones of the Comanche series, which 
form the western rim of the Marathon Basin. 
Near Marathon and to the west the Glass Mountains are conspic- 
uous to the north. The name is a translation of the Spanish Sierra 
del Vidrio, said to have been given because of the glassy appearance 
of the limestone cliffs when seen from a distance. According to 
Hill,” however, the name Glass Mountains was first used for the 
novaculite ridges of the Marathon Basin and was later transferred 
® R. T. Hill, a pioneer in the geologic | ography of Texas gave the first clear 
exploration of Texas, established the conception of the relations of the 
classification of the Cretaceous rocks | Edwards Plateau and of many other 
in that State and mapped them over a | important topographic features of the 
wide area. His work on the physi- | State. 
