40 [APPENDIX 



determine to a certain extent the age of the volcanic series which has 

 disturbed them, and fixes that age posterior to the formation of the latest 

 of the groups. 



CHANGES OF LEVEL AND KIYEK TEERACES. 



The valley sections of this State present a general uniformity of char 

 acter in their superficial structure, wherever found ; their surfaces are 

 distinctly marked by a regular series of minor elevations, which give 

 them the terraced form so peculiar to those sections. The face of these 

 terraces'are of different heights, and the surface of each is found to have 

 a gent|e inclination toward the streams that flow through them. In some 

 parts of the " great valley " there are to be seen a range of hills having 

 flat summits, which on examination are proved to have been the shores 

 of an inland sea; these usually arise from the higher portions of the 

 upper terraces, and where they are found near the borders of the plain, 

 they present often trifling evidences of excessive subterranean action. 

 These "tables" when found on the immediate borders of the plains, do 

 not appear to have participated in the more violent disturbing forces 

 found in the interior ; they are usually from four to five hundred feet in 

 height, while those farther to the east attain an altitude frequently of 

 more than two thousand. 



Immediately succeeding these, the first terraces of the valleys appear, 

 and from the observations of different travelers, we learn that they are 

 continuous into the Territory of Oregon, and probably beyond that 

 point ; while south of California their existence is known to the northern 

 boundary of the Province of Sinaloa in the Republic of Mexico. In 

 these we see the evidences of gradual and probably persistent elevation 

 over an extent of country nearly two thousand mibs in length, and in 

 the present state of our knowledge, must be regarded as part of one of 

 those great continental elevations that has occurred during the compara 

 tively "recent history of the world. This State is situated nearly in the 

 centre of this line, and from its position must partake to a greater or 

 less extent in all the general changes of level that nay occur on either 

 side of it; and all -observations which have been made within the last 

 ten years have only tended to confirm this fact. 



Mr. Dana who has given more attention to the foimations of the valley 

 sections of the Pacific Coast, and who probably hac better opportunities 

 for observation from San. Francisco to the north, in speaking of them, 

 says : " We traced these terraces from the Cowlitzto the mouth of the 

 Sacramento, along many of the smaller streams as well as the rivers. 

 There appears to be but two ways of accounting for these terraces, either 

 lakes have existed along the rivers % which have birst their barriers, or 

 the rivers have excavated the country in conseqrance of an elevation. 

 The existence of lakes throughout a whole courtry, connected with 

 all its rivers, is highly improbable, and required for its proof the strong 

 est evidence. Rivers cut out their channels by a gradual process, as a 

 country is raised above the ocean, forming with few exception a complete 

 drainage for the land. Lakes could not exist, therefore, to the universal 



