4 INTRODUCTION. 



The remarks of Prof. Hitchcock on the age of the drift (p. 152) may, 

 but possibly do not, apply to the Llano drift, since Dr. Shumard does 

 not mention any of the silicified wood as coming from the drift observed 

 on top of the Llano. 



Prof. Hitchcock says: 



' ' I have been lead to suspect that what Dr. Shumard calls drift may 

 be only a newer portion of the Tertiary strata, although, as already re- 

 marked, silicified wood is found in almost all the fossiliferous formations. 

 All of the specimens sent by you, however, with one exception, are dico- 

 tyledonous. They resemble not a little the fossil wood from Antigua, 

 and the desert near Cairo, in Egypt, both of which deposits are Tertiary. 

 One specimen is a beautiful example of monocotyledon, a cross section 

 showing vessels of the shape of a half or gibbous moon. This fact shows 

 that the climate was warm enough for trees analogous to the palm tribe to 

 flourish; yet the great predominance of dicotyledonous forms shows a 

 close analogy with the existing vegetation of the southern part of our 

 country ; nor is there evidence in these specimens of a temperature above 

 that now existing in our southern States, since several species of palms 

 occur there." 



Captain Marcy himself makes this statement in regard to the same 

 locality: 



' ' The geological formation of these bluffs is a red indurated clay, 

 resting upon a red sandstone, overlaid with a soft dark gray sandstone, and 

 the whole capped with a white calcareous sandstone, the strata resting 

 horizontally, and receding in terraces from the base to the summit." * 



Following this expedition came the surveys of the Pacific Railroad 

 route. In volume II of this report Mr. W. P. Blake reports on the geol- 

 ogy of the route along the thirty-second parallel from the collections of 

 the party under Captain Pope. Of the Llano Estacado he says (p. 17): 



' ' The specimens of the rocks from the Llano Estacado have a general 

 resemblance to each other, and show the nearly uniform nature of the 

 geological formation. They consist for the most part of light colored, 

 whitish, or gray calcareous sandstones, with specimens of compact amor- 

 phous limestone, which resembles the specimens containing the Cretaceous 

 fossils from the Big Springs. Three or four specimens consist of sand 

 and gravel united by a calcareous cement, and looking as if these mate- 

 rials had been exposed to the infiltration of water highly charged with car- 

 bonate of lime. * * * These have a very modern aspect, 

 and much resemble the sandstones and conglomerates of the Tertiary age. 



*p. 50. 



a 



