188 THE SALT ROCK. 
southwestward, on the main Red Fork. “The 
whole cove on the right of the two forks of 
the river,” says Capt. Boone, “appears to be 
one immense salt spring of water so much 
concentrated, that, as soon as it reaches the 
point of breaking forth, it begins depositing 
its salt. In this way a large crust,or rock is 
formed all over the bottom for perhaps 160 
acres. Digging through the sand for a few 
inches anywhere in this space, we could find 
the solid salt, so hard that there was no means 
in our power of getting up a block of it. We 
broke our mattock in the attempt. In many 
places, through this rock-salt crust the water 
iled up as clear as crystal. ..... but so 
salt that our hands, after being immersed in 
it and suffered to dry, became as white as 
snow. Thrusting the arm down into these 
holes, they appeared to be walled with salt as 
far down as one could reach. The cliffs which 
overhang this place are composed of red clay 
and gypsum, and capped with a stratum of 
the isfier: 2 oS We found this salt a little 
bitter from the impurities it contained, proba- 
bly Epsom salts principally.” As it is over- 
hung with sulphate of lime, and perhaps also 
based upon the same, might not this ‘salt 
rock’ be heavily impregnated with this mine- 
ral, occasioning its excessive hardness? Capt. 
ne also speaks of gypsum in various othet 
places, both north and south of this, during 
his travel. 
Mr. Sibley (then of Fort Osage), who was 
quite familiar with the western prairies, visit 
