14 STOCK RANGES OF NORTHWESTERN CALIFORNIA. 



altitude is about 1.600 feet. Back from the coast, where it passes into the higher 

 and more monntainons tract of central and eastern Mendocino County, it has an 

 elevation of about 2.100 feet. On entering Humboldt County several sharp peaks 

 rise abruptly above the general level of the dissected plateau to altitudes of from 

 3.000 feet to 4.000 feet, but remnants of plateau clearly encircle these and give 

 their middle slopes a distinctly terraced aspect. 



It is evident that northward of the fortieth parallel of latitude the forces which 

 effected the evolution of the original plain have made but little headway as com- 

 pared with the coastal region to the south of the same line, or they had been inter- 

 rupted in their work by orogenic disturbances. The plain in Humboldt County 

 represents no broad expanse, as in Mendocino and Sonoma counties, but may be 

 followed in between an open cluster of mountain peaks and ridges. The present 

 reconnaissance establishes the fact of its extension as far as the Bear River ridge. 

 It doubtless extends up the coast, however . far beyond the limit set to (my) 

 exploration. 



That this great dissected plateau represents an ancient peneplain which has 

 been uplifted from a nearly base-leveled condition to its present altitude seems 

 beyond question. The rocks of which it is composed are of various ages, of vari- 

 ous degrees of hardness, and have been throughout the region so disturbed that 

 their original horizontal condition is practically nowhere to be found. The sur- 

 face of the ancient peneplain consists of the beveled edges of the upturned strata. 

 On the summit of one of the characteristic ridges of the plateau between Usal 

 and Kenny numerous waterwom pebbles were found at an elevation of about 

 1.600 feet. 'which can only be interpreted as remnants of the stream gravels of 

 the ancient peneplain. 



CLIMATOLOGY. 



The following data are compiled from the annual summaries of the 

 Weather Bureau: 1 



The only stations within the region from which we have any clima- 

 tologieal data are: 



In Mendocino County: Point Arena and Fort Bragg on the coast. 

 Ukiah and Cahto in the interior. 



In Humboldt County: Upper Mattole. Cape Mendocino. Humboldt 

 Light and Eureka on the coast, Hydesville in the Interior. 



In Del Xorte County; Cresent City on the coast. 



From the interior plateau belt, proper. Ave have no data. 



Temperature. — The mean annual temperature for the three years 

 1897-1899, as recorded in the annual summaries of the Weather 

 Bureau, was 50 degrees F. The highest in 1899 was 108 degrees in 

 the interior at Ukiah, on July 2 and other days, and S3 degrees on 

 the coast aj Crescent City on September 15. The lowest was 20 

 degrees at Ukiah on February 5, and 23 degrees at Crescent City on 

 February 4. 



The last killing frosts in spring were: February 5, at Ukiah; Feb- 

 ruary 7. at Eureka: May 9, at Cahto: and June 19 at Crescent City. 

 The first killing frosts in autumn occurred on October 14. at Crescent 

 City; October 25. at Cahto: December 13 at Eureka and Ukiah. 



a TJ. S. Dept. of Agriculture. Weather Bureau. California Section of the Climate 

 and Crop Service. Annual Summaries for 1897. 1898. and 1899. San Francisco. 



