174 GEORGE OTIS SMITH 



On the west side of the Columbia, opposite the mouth of Crab creek, the 

 continuation of the mountain is bounded on the north, not by a cliff, but a steep 

 slope. The mountain shows no outcropping horizontal ledges, but rising 

 through the mantle of soil sloping back on the spurs and forward in the gulches 

 can be traced the outcrop of one or more especially resistant beds of black 



lava, having a dip a little steeper than the slope At another point 



twenty miles east of the mouth of Crab creek, the slope of the mountain was 

 examined again and a similar state of things observed The evi- 

 dence demonstrates that there is here a sharp flexure and not a fault. 



While the fact is not proven beyond doubt, I believe that this flexure, 

 observed both east and west, was once continuous along the entire front of 

 Saddle mountain, that the cliff along lower Crab creek is the product of ero- 

 sion, and that the flexure is here concealed below the sediments in Crab creek 

 bottom. 



This citation of conclusions as to the orography of central 

 Washington based upon reconnoissance observations and their 

 comparison with the results of later and more detailed field work 

 is believed to be justified by the result gained. Further evidence 

 as to the true type of uplift is presented in the accompanying 

 structure sections, Fig. i. These are drawn to scale, and the 

 structural features indicated are based upon dips observed along 

 the line of section, and upon the general form of the different 

 anticlines as exposed in the Yakima canyon section. The oppor- 

 tunity for direct observation of structure afforded in these gaps 

 cut by Yakima river is exceptional and entitles the structure sec- 

 tions to considerable credence. The use of the scale i : 125,000 

 without vertical exaggeration renders the relief much less promi- 

 nent than it appears to be in the field, but it is believed that a 

 more accurate conception of structure can be obtained from these 

 sections than from many drawn to illustrate the Basin range type, 

 in which, as the author states, "the vertical scale is exaggerated 

 and no attempt is made to represent the structure of the oro- 

 graphic blocks." 



The type of deformation existing in central Washington is 

 of interest in that enough is known of the geologic history to 

 state the amount of load under which the rocks were flexed. Men- 

 tion has been made of the two periods of uplift. In the earlier, 

 which is believed to have been during either late Miocene or early 

 Pliocene, the Yakima basalt may have been covered by 2,000 



