THE GRAND COULKK 



353 



recede in a series of great platforms, 

 formed by the successive lava flows, to 

 the upper level which forms the floor of 

 the Upper Coulee, upon which the town 

 is situated. The walls of this east 

 branch of the Lower Coulee show 

 columnar jointing particularly well. 



Looking westward down the east 

 branch we saw Deep Lake far below, 

 like a winding river in a deep canyon. 

 In the distance looms the great west 

 wall barrier. The colors of Deep Lake 

 vary greatly with the time of day, rang- 

 ing from a peculiar emerald-green to a 

 deep bluish-green, but the lake is always 

 wonderful, and flanked by the vari- 

 colored basalt rock it forms a scene that 

 should be preserved in color by some 

 artist. 



\\ e decided to take a day trip north, 

 in the Upper Coulee, to Steamboat 

 Rock, a distance of about 20 miles. On 

 starting north from the town we saw 

 perched on the top of the west wall a 

 short distance back from the edge a 

 great basalt block as large as a house, 

 which was evidently transported a short 

 distance and left by the ice sheet which 

 spread over the western part of the Big 

 Bend region. This was Pilot Rock, a 

 landmark easily seen for many miles to 

 the east. Five miles to the north the 

 inclined lava beds of the east wall rise 

 out of the plain and flatten out, form- 

 ing the eastern wall, which has an aver- 

 age height of about 450 feet. We noted 

 that the edges of the inclined lava beds 

 are truncated by the present surface of 

 the plain. This shows that after the 

 warping and irregular uplift, the region 

 \vas greatly eroded and worn down 

 nearly to a plain before the final uplift 

 to the present elevation. Going north 

 on the flat floor of the Upper Coulee we 

 passed a few long, narrow lakes lying 

 in swampy depressions near the foot of 

 the west wall. The lakes have a dense 

 growth of rushes about their shores, 

 and usually a fringe of white alkaline 

 deposits, where the water has evap- 

 orated and left the salts held in solution. 

 About ten miles to the north of the 

 town the Upper Coulee makes a bend 

 and we got our first view of Steamboat 

 Rock, which looks like the hull of a 

 great battleship floating toward us. The 



Coulee narrows to a width of about a 

 mile a short distance below the r< 

 and then widens out until in the viciniu 

 of the rock it is between three and four 

 miles across. Steamboat Kock is a mesa 

 or table mountain of horizontal lava 

 beds g.bout 4-">() feet high and one and a 

 half miles long by one mile wide. < )n 

 the floor of the Coulee about a half 

 mile north of the rock is a fine ranch, 

 with an orchard and garden, where a 

 stop for lunch was made. While re-t 

 ing in the shade of the numerous trees 

 about this ranch we enjoyed a splendid 

 view of the great mass of Steamboat 

 Rock. . Time permitting, we extended 

 our trip ten miles, to the northern end 

 of the Grand Coulee, where we looked 

 down on the mighty Columbia River 

 flowing in its deep gorge, which is now 

 cut several hundred feet below the level 

 of the floor of the Coulee. The Coulee 

 north of Steamboat Rock narrows again 

 and the floor becomes very uneven as 

 the lava cover becomes thinner, and the 

 old granite surface with its hollows and 

 knobs is exposed. By ascending to the 

 top of the east wall of the Coulee we 

 had a very grand and comprehensive 

 view of the northern part of the Coulee, 

 and looked down over 1,000 feet to the 

 waters of the Columbia River. To the 

 northwest we saw through the blue haze 

 the mouth of the Okanogan valley, bor- 

 dered by low mountains on the west. To 

 the north of the river rises a granite 

 range of low mountains, and eastward 

 the slightly rolling lava plains stretch 

 to the horizon. 



The drainage of the Grand Coulee is 

 for the most part underground. The 

 chain of lakes occupying the western 

 border of the Upper Coulee are of vary- 

 ing degrees of salinity. In most cases 

 there is no visible connection between 

 the lakes, and they have no visible 

 drainage outlet. The lakes of the Lower 

 Coulee are fresh at the north and 

 strongly saline at the south. Some of 

 the northern lakes overflow in the rainy 

 season and drain south into the more 

 saline. Soap Lake is the most saline of 

 the chain, and the waters have been 

 analyzed and found to be rich in sodium 

 salts, chiefly the carbonate and sulphate. 

 Moses Lake, farther south, is compara- 



