176 J. LeConte—Old River-beds of California. 
Art. XXIIL—The Old River-beds of California ; by JosEPH 
LEConrE. 
[Read before the National Academy of Sciences, Oct. 29, 1879.] 
OLD river-beds are found in nearly all countries which have 
been affected by drift-agencies. In nearly all such countries, 
too, these old beds are filled to great depths with river deposit. 
ut the old river-beds of California are in several respects en- 
tirely unique. In most other countries, as for example, in Hu- 
rope and Kastern United States, the new or present river-beds 
occupy the same position as the old; while in middle Califor- 
nia the rivers have been displaced, by lava flows, from their 
former position and compelled to cut entirely new channels. 
gain: in certain portions of Europe and in Eastern United 
States, the old river-beds are broad, deep troughs, filled some- 
times several hundred feet deep with detritus, into the upper 
parts of which the present mnch shrunken streams are cutting 
their narrower channels on a Azgher level; while in California 
the displaced rivers have cut their new channels 2000 to 3000 
feet deep in solid slate, leaving the old detritus-filled channels 
far up on the dividing ridges. In northeastern United States 
the drainage system has remained substantially unchanged 
since early Tertiary, or even still earlier times ; while in middle 
California the Tertiary drainage system seems to have been 
obliterated and the streams have been compelled to carve out 
to a much deeper level an entirely new and independent drain- 
age system, having the same general direction but often cutting 
across the former. In the one case the old beds wnderlie the 
beds of California, consisting as it does largely of sears and 
bowlders, compared with the fine silts which fill t : 
channels of the Eastern coast, and we will see how marked 18 
the contrast in many respec : 
For all that is known concerning the old river-beds of Cali- 
fornia, we are up to the present time almost wholly indebted to 
Professor Whitney. His valuable investigations on this sub- 
ject were published in the first volume of the Geological Sur 
vey of California in 1865. He has also recently published a 
fuller description and a complete map of them. His views 
have therefore been before the scientific public for many yea! 
and are so well known that a bare enumeration of their mai? 
