672 OREGON AND NORTHERN CALIFORNIA. 
hundred and fifty miles from the sea; thus far, they were examined 
by the writer; and they appeared to extend up the larger branch, as 
far beyond as the eye could reach. At the point here referred to, they 
were as high as at any point lower on the river, having nearly the 
same elevation, in all parts examined, above the existing level of the 
river. The flats were many miles in width, until reaching the 
Caquines Straits, near the Bay of San Francisco, and here is the only 
place where any barrier could have existed. In the first place, a per- 
manent barrier of at least four hundred feet would be required to set 
the waters back so as to cover the upper terrace one hundred and fifty 
miles above the mouth of the river; and in the second place, such a 
lake should have its surface slope like the present bed of the river, for 
that is the fact with the level of the terrace,—of course an impossi- 
bility. Wherever the bed of the river was four hundred feet above 
the sea, there the terraces should die out, or have the level of the 
present lower flat, instead of having a corresponding height along its 
whole course, or, perhaps, a greater one in the upper part of the valley. 
It is therefore impossible that one or many lakes should accomplish 
such a result as we have before us; it is the proper effect of river 
floods, and the terraces must be received as indicating a change of 
level in the country. 
The utter inability of the lake or barrier theory, will be farther 
evident when the extent of terraces over the United States, east of the 
Rocky Mountains, is understood. Unfortunately, this branch of 
American geology has not yet received the attention it deserves. 
Still we know the general fact, that there are terraced alluvial plains 
along all the rivers that have been examined on this point. The 
writer has traced them for a long distance up the Connecticut, from 
Massachusetts into New Hampshire, and observed that they have no 
less height up the river than below, and have a near parallelism 
with its surface, instead of conforming to the level that the surface of 
a lake or lakes would have. He observed particularly that where the 
river passed through rocky gorges, a fit place for a barrier, if there 
had been such, the terraces were at the same height above and below 
the gorge, although wanting along these narrow places, where they 
would necessarily have been washed away by the river, if they had 
existed there. Even along the tributaries, far towards the White 
Mountain Notch, similar terraces existed. In the case of this river, 
no lake or lakes could account for the facts; and we feel persuaded 
that in most others over the land, this is also true. The country 
