398 GEOLOGY OF NORTHWESTERN TEXAS. 



The changes that were taking place in the geological history of the world 

 at that time were unfavorable to the production of a heavy growth of vege- 

 tation and the deposition of material for making coal beds. This in itself 

 would not be of much importance in determining the change from the Coal 

 Measures to the Permian, but only shows that a change of some kind was 

 taking place ; and when one has passed up into the overlying beds but a short 

 distance the difference is so apparent that the most casual observer can see 

 that he has left the Coal Measures behind and has come upon something en- 

 tirely different. 



THICKNESS. 



For quite a while it was thought that the Permian was merely the round- 

 ing off' of the great Paleozoic area, and that it would only be found in nar- 

 row strips along the edge of the Carboniferous formation, but such can no 

 longer be said to be the case, for the Permian has been found in the United 

 States extending over a vast region, and is more than two thousand feet thick. 

 In Texas the whole of the beds placed in the Permian are at least five thou- 

 sand feet thick. These beds must have required a long period of time for 

 their deposition, and the formation is entitled to be represented as a series in 

 geological nomenclature. 



LITERATURE. 



In considering the Permian in Texas it may be well enough to state what 

 has been written of this formation by others who have visited the region 

 heretofore. 



The first report of the Permian in this country was made by Prof. Jules 

 Marcou, who traveled across the country from Fort Smith, Arkansas, to Los 

 Angeles, California, between June, 1853, and March, 1854. In his resume of 

 that trip, published in 1854 in " Report of Explorations for a Railroad Route 

 near the 35th Parallel of Latitude," Washington, he says: "Immediately 

 after crossing Delaware Mount * * * we met with horizontal beds of 

 red and blue clay that belong to another geological epoch. This new forma- 

 tion corresponding to that which European geologists have agreed to call the 

 Trias." 



In a paper published in 1858 he says of his name Trias, given to this lo- 

 cality: "I have always strongly suspected that the New Red Sandstone be- 

 tween Delaware Mount and Beavertown was of Permian age. Having found 

 no fossils, and being the first geologist to enter these regions, I was not able 

 when in the field to declare exactly the age of those strata. All that I knew 

 then was, that after having left the Carboniferous limestone of Delaware 

 Mount I entered upon strata belonging to another and younger formation; 



