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TOPOGRAPHY OF THE PACIFIC COAST.
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Deformation of the baselevel.

It is evident that since the Miocene there have been great changes of level in northern California, for instead of the original baselevel of the erosion, we have now prominent mountain ranges, whose sides are furrowed by the deep cañons of the rejuvenated streams.

The deformation of the baselevel may be studied along two lines of evidence: (1) by tracing the present variations of altitudes in the original baselevel, which must have had a very gently sloping surface itself, and (2) by tracing the deformation of the Ione deposit which, when laid down, must have been below sea level at a lower altitude than the baselevel, because deposited in the water body upon its border. Each line of evidence should corroborate the other and render conclusions concerning the deformation more trustworthy.

It is impossible to tell from what is known at present the original inclination of the baselevel. It is evident, however, that it must have been considerably less than one degree, for at that angle streams generally erode their beds much more than their banks, and cut cañons.

Upon the western edge of the baselevel, at the foot of the Klamath Mountains in Tehama county, the altitude is nearly 2,300 feet, while upon the eastern edge it is considerably less than 1,000 feet, giving the old plain in the Greasewood hills a slope of 100 feet to the mile to the eastward. Across this plain the present streams flow in cañons 300 to 400 feet deep, and they are still cutting. The cañons in general are deepest to the westward and gradually run out to the Sacramento river in the newer deposits which fill the valley. It is evident that since the baselevel was formed, it has been affected by differential elevation in the uplifting of the Coast Range and Klamath Mountains, just north of the fortieth parallel, to the extent of over 2,000 feet, and if we may judge from the traces of the baselevel seen at Shower's pass and South Fork Mountain, the upheaval in the Klamath Mountains has been much greater. It has long been

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