14'6 Expedition to the 



times so frequent, as to render the walking difficult. It is co- 

 vered with long and slender prickles, capable of inflicting a 

 painful and lasting wound, which is said to prove ruinous to 

 the feet of the blacks in the West Indies. The cacti and 

 the bartonias had now disappeared, as also the yucca, the 

 argemone, and most of the plants which had been conspicuous 

 in the country about the mountains. The phytolacca c/ecandra, 

 an almost certain indication of a fertile soil, the diodia te- 

 tragona^ a monarda, and several new plants were collected in 

 an excursion from our encampment. The red sand-rock is 

 disclosed in the sides of the hills, but appears less fre- 

 quently, and contains less gypsum than above, though it 

 still retains the same peculiar marks distinguishing it as 

 the depository of fossil salt. Extensive beds of red argilla- 

 ceous soil occur, and are almost invariably accompanied by 

 saline eflSorescences, or incrustations. We search in vain, both 

 in the rocks and the soils for the remains of animals, and it is 

 rare in this salt formation to meet with the traces of organic 

 substances of any kind; the rock, itself, though fine and com- 

 pact, disintegrates rapidly, producing a soil which contains so 

 much alumine as to remain long suspended in water, 

 tinging with its peculiar colour all the rivers of this region. 

 It has been remarked that the southern tributaries of the 

 Arkansa, particularly the Canadian, the Negracka, and the 

 Ne-sew-ke-tonga, discharge red waters, at the time of high 

 freshets in such quantity as to give a colouring to the Ar- 

 kansa quite to its confluence with the Mississippi. From this 

 it is inferred that those rivers have their sources in a region 

 of red sandstone, whose north-eastern limit is not very far re- 

 moved from the bed of the Arkansa. We attempted to take 

 sets of equal altitudes, but failed on account of a trifling in- 

 accuracy in our watch. The variation of the magnetic nee- 

 dle was found to be the same as on the 25th; namely, 11° 

 30' east. 



Our hunters had been sent out in quest of game, as not- 



