iv INTRODUCTION. 



pecan, mulberry, oak of diflerent species, Cottonwood, cedar, osage orange, with 

 many other species, and thickly interspersed with large cane. These prairies are 

 very distinct in their character from those of the uplands, and only resemble them 

 in being destitute of timber. Ascending northwardly from the river valley, we 

 pass over an elevated timber region, generally level, diversified with ridge and 

 valley, finely watered, soil of several varieties, sandy with pine, clay loam with 

 oak, hickory, and dogwood, and occasionally a tract of prairie. 



" Washington, the county town, is situated on a sandy pine hill, in about the centre 

 of the county, in latitude 33° 42', one hundred and fifty miles west of the Missis- 

 sippi, fourteen miles northeast from Fulton, on Red River, and on an elevation of 

 about six hundred feet above the bed of Red River, immediately south. To 

 the north and west of the town are the upland prairies. These prairies exhibit a 

 very interesting appearance in a geological point of view. Where they join upon 

 the timbered land, the change is abrupt, from tall timber to naked rock. Tall 

 pine, oak, and hickory, with their roots imbedded in a tough ferruginous clay, 

 grow to the very margin, the line of junction resembling the shore of a lake. 

 The naked prairie is the soft limerock that underlies, at various depths, this 

 whole southwestern region. It has been penetrated by the auger, in attempting 

 to procure water by boring Artesian wells, to the depth of four hundred and 

 fifty feet, without any material change in its character, except occasionally a thin 

 stratum of sandstone. The rock is soft enough to be cut with a knife, and yet 

 cisterns excavated in its substance will hold water and preserve it in purity during 

 any length of time. The chemical composition, so far as I have been informed, is 

 85 per cent, of carbonate of lime, with a small proportion of silica, and intimately 

 combined with alumina, so that, when exposed to the atmosphere, the moisture 

 absorbed causes it to fiiU to powder. The naked prairie has the appearance of 

 having been denuded of its superstratum of clay and sand, and the surfixce pro- 

 duces a slight vegetation, which, being loosened by the action of frost, is ever 

 ready to be washed by the rains to lower grounds, forming a soil of increasing depth 

 as it descends, until, in the valleys, it sustains a growth of heavy timber and cane 

 — a deep, black soil, composed essentially of lime and vegetable mould. Many 

 of these valleys, or river and creek bottoms, are of considerable extent, and are 

 continually increasing in width and depth of soil, by accessions of alluvium from 

 higher grounds. This soil has the peculiar property of retaining moisture, and sus- 

 taining a drought without material injury, that would be fatal to crops on sandy 

 uplands. The soil is scarcely surpassed in fertility, yielding equally well all the 

 varied products of the North, and the cotton of the South. 



" During the heat of summer, continued refreshing breezes pass over the elevated 

 region, which render the climate pleasant and healthful." 



The leductions of the observations were made at the Smithsonian Institution. 



JOSEPH HENRY, 



Secretary S. I. 



