ANCIENT STREAM CHANNELS. 157 



portion of Lahontan history that witnessed the accumuhition of the upper 

 clays; and since the walls of the channel are composed of lacustral sedi 

 ments, the inference is drawn that it was excavated during an inter-Lahon- 

 tan period of desiccation. It will appear, as we progress with our history, 

 that this is but one of a number of independent lines of proof which show 

 that Lake Lahontan liad two high-water stages, separated by a time when 

 it was greatly lowered by evaporation, and perhaps reached absolute dryness. 



The ancient chaimels, now dry and abandoned, similar to the one con- 

 necting Carson Desert and the desert basin south of it, occur at the northern 

 end of Pyramid Lake Valley; one of these leads to Honey Lake Valh }■ 

 and the other to Smoke Creek Desert. The former, known as Astor Pass, 

 was never deeply excavated, showing that tlie valley in which Honey Lake 

 is situated must have been an independent water-body during a large part 

 of the Quaternary. The second, however, is a pass, now partially obstructed 

 by gravel embankments, which must have been a narrow strait during the 

 greater part of the Lahontan period. The bottom of this pass is on a level 

 with the thinolite terrace in Pyramid Lake Valley, as shown by aneroid 

 measurements, and is thought to have regulated the water in that valley in 

 such a manner as to bring it frequently to the same level. This would be 

 accomplished by allowing it to escape, at a certain horizon, on to the Smoke 

 Creek Desert. It may be that this is the reason for the great strength of 

 the thinolite terrace about Pyramid Lake. Another channel of a similar 

 character, now known as the Ragtown Pass, connects the Carson Desert 

 with the desert valley in which the Eagle Salt Works are situated. All 

 these channels were in existence before the deposition of dendritic tufe, but 

 the proof that they were excavated in lacustral clays is less definite. It is 

 probable that some of them were occupied by streams before the first rise 

 of the ancient lake. In some instances they have become partially re-exca- 

 vated during the present period of desiccation, but usually they are still 

 occupied by the upper clays. 



Other channels of this character have been examined in the Lahontan 

 basin, but their features are not so clearly defined as in the examples 

 described above, and their bearing on the history of the former lake is con- 

 sequently less definite. 



