Hershey.] 



The Hirer Terraces of the Orleans Basin. 



471 



large trees and slides away from the lower sides, thus furnishing' 

 a means of a fairly good estimate of the rate of movement of 

 the surface debris. Trails which were established fifty years 

 ago, and not repaired since, have a curious and aggra- 

 vating serpentine course. Where they passed above trees 

 they remain in their original position, but between the trees they 

 have worked down the slopes from several to ten feet. By a 

 careful study of these trails it is learned that there has been a 

 continued movement of the debris down the slope, but it has 

 been very slow. Trails which are not used during the winter 

 months are not severely injured unless locally by landslips. 

 Abandoned toils on steep slopes are not obliterated for scores 

 of years. Large trees occur on narrow mountain summits, and 

 demonstrate that in general these summits are not lowered one 

 foot in a century. If the Klamath Canon was now being 

 enlarged at a rate sufficient to have produced it in 100,000 

 years, the timber could not maintain a foot-hold on its slopes 

 and it would be uninhabitable. The Pleistocene erosion through- 

 out the central portion of the Klamath region is equivalent to 

 the removal of a sheet of very resistant rock from 500 to 2,000 

 feet thick, and all of this material was passed out through the 

 mouth of a single stream that, before the arrival of the placer 

 miners, was "clear as crystal" nearly all the year. One million 

 years is a conservative estimate of the time required. 



CORRELATION. 



For the purpose of correlation, only three of the terraces are 

 important, namely, the highest, the 120-foot and the lowest. 

 Remnants of this system occur in all the principal valleys of 

 the Klamath region, but reach their finest development on the 

 western slope, near the coast. 



The small Modern canons are characteristic of the country 

 west of a line whose course seems to be a little east of north, and 

 whose position is just west of Scott Valley, nearly midway 

 between Trinity Center and Summerville, and traverses the 

 Trinity River, probably near Junction City. This is the axis of 

 the uplift to which these canons are due. Now, two large rivers, 

 the Klamath and Trinity, rise east of the axis and cross it. The 



