436 PUGET SOUND AND OKONAGAN. 



On the 12th, they reached the Grande Coulee. The common suppo- 

 sition relative to this remarkable geological phenomenon is, that it has 

 once been the bed of the Columbia, and this is what would strike every 

 one at its first view; but, on consideration, it is seen that it is much too 

 wide, and that its entrance is nearly choked up by the granite hills, 

 that do not leave sufficient space for the river to flow through. The 

 walls of the Coulee consist of basaltic cliffs, similar to those of the 

 Palisades of the Hudson, seven hundred and ninety-eight feet high ; and 

 where it was crossed by the party, it was three miles wide ; but, a few 

 miles farther to the south, it narrowed to two miles. Its direction was 

 nearly north and south, for a distance of at least fifteen miles. In 

 places, the cliffs were broken, and appeared as though tributary valleys 

 had been formed, in like manner, with perpendicular walls, though but 

 of short extent. In the northern portion of it were several granite 

 knolls, resembling islands, capped with basalt, and called Isles des 

 Pierres. The bottom of the Coulee is a plain, having some irregu- 

 larities, but in places, for two miles together, to appearance it was 

 perfectly level. There are in it three lakes : one on the top of the west 

 border, another after descending, and a third between two of the granite 

 islands. The last of these was the largest, being about a mile long, 

 but is not more than three hundred feet broad : these lakes have no 

 visible outlets. Although the soil abounded in the same saline efflore- 

 scence that had been remarked on the high prairie, yet the lakes were 

 found to be fresh, and wild ducks were seen in great numbers. In other 

 spots, the earth was damp and overgrown with a rank grass, of the 

 same kind as that growing on the prairie. Next to this, the wormwood 

 predominated. 



In the level places the earth was much cracked : incrustations were 

 abundant, which, sparkling brilliantly in the sun, gave the plain some- 

 what the appearance of being covered with water. Specimens of 

 these were procured, the analysis of which will be found in the 

 Geological Report. 



The granite islands, above spoken of, were found to be seven hundred 

 and fourteen feet high. Mr. Johnson named the southern one the 

 Ram's Head. Dr. Pickering, who visited the north part, found no 

 regularity of structure. All were satisfied, after leaving the Coulee, 

 that it had been the seat of a lake, in the northern branch of which, 

 some convulsion had caused a breach, through which it had discharged 

 itself into the Columbia. If the Columbia had ever flowed through this 

 channel, it must have worn the rocks, but they exhibit no signs of any 

 such abrasion ; and yet it seems remarkable, that the Coulee had 

 extended from one point of the river to another, and, with the excep- 



