BOTANICAL INFORMATION. 31 



Following upon the cursory description of Missouri terri- 

 tory, will come the 



V. — Mountainous, or Intermediate Region, dividing natu- 

 rally into three more or less distinct groups, as : 



1st. The great Rocky Mountain chain in connexion with the 

 Wind-river Mountains ; 



Indly. The range of the detached granite mountains on the 

 uppermost different forks or arms of the Platte ; and 



3rdly. The Black Hills, or Black Mountains, in connection 

 with the hills- of the. north and south fork of Platte River. 



The apparent geological features follow in form of a 

 synopsis ; stating the different characters and compositions 

 recognized, from the great central chain down to the Missouri 

 limestone near the mouth of the Platte. 



1st. Central chain and Wind-river Mountains; the 



A. — Highest ; consisting of hard granite, bluish or whitish, 

 rarely reddish, in very steep or nearly vertical layers ; here and 

 there forming high peaks. Surface smooth, marked by 

 cracks into large, mostly irregular, often somewhat rhomboid 

 blocks ; the grain dense and even. Parallel with, or radiating 

 off from these are : 



B. — Lower mountains of the same granite, but with a 

 rough surface, divided into loose masses or vast blocks, 

 which likewise have sometimes a rhomboid form ; sometimes 

 with nearly horizontal layers at the base, but always divided, 

 as if rent by a shock. The basilar blocks are not unfre- 

 quently of a coarser grain, laminated, whole parts con- 

 sisting of large feltspar crystals. (A common variety 

 of granite occurs on the western slope of these mountains ;) 

 alternating with these are : 



C. — High oblong edge-topped mountains, of syenitic 

 granite ; their average height about 1500 feet. Their surface 

 is so broken to small somewhat wedge-formed fragments, 

 as to resemble artificial heaps of stones. They are traversed 

 by vast dykes of dense basaltic rock and greenstone; of 

 a blackish colour, firmly connected with the heterogenous 

 masses, and have, at the lowest, an (easterly) inclination 



