March 14, 1902.] 



SCIENCE. 



413 



able and interesting bodies of fresh water 

 in the west. It is situated in an ancient 

 valley upon the eastern slope of the Cas- 

 cade range in northern Washington. The 

 lake has a length of about 60 miles and a 

 width of one to two miles. It has an eleva- 

 tion of 950 feet above the sea level and a 

 depth of about 1,400 feet. The country 

 surrounding the lower end of the lake is 

 quite open and contains numerous settlers, 

 but through the greater portion of its 

 length it is inclosed by mountains which 

 rise quite precipitously 3,000 to 5,000 feet. 

 The valley in which the lake lies has had 

 an interesting history. It was occupied in 

 quite recent times by one of the largest 

 glaciers upon the eastern slope of the Cas- 

 cade range. Previous to that there was 

 another lake here, but at a somewhat lower 

 level. The earlier lake was probably raised 

 but slightly above the level of the Colum- 

 bia river, into which it must have emptied. 

 In the opinion of the author the great depth 

 of the lake is due not to the erosion of the 

 glacier, but to the fact that it was the bed 

 of a stream, and was cut out chiefly by 

 stream erosion. The glacier undoubtedly 

 enlarged the valley somewhat and may have 

 deepened it a little. If this view is the 

 correct one the valley in which the lake 

 lies must have been eroded at a time when 

 the level of the land with respect to the 

 ocean stood many hundreds of feet higher. 

 The Columbia lava plateau would interfere 

 with the drainage of such a valley, so that 

 it must have been excavated prior to the 

 formation of the plateau. The lake is held 

 at its present level of 325 feet above the Co- 

 lumbia river, from which it is distant only 

 three miles, by a morainal dam. The lower 

 end of the lake is shallow, but as far as 

 knoAvn to the author there is no reason to 

 suspect that bedrock woiild be encountered 

 at about the level of the Coljimbia river, 

 which would be the case if the bed of the 

 lake had been dug out by the glacier. 



Lake Quiberis, an Ancient Pliocene Lake 

 in Arizona: Wm. P. Blake, Tucson, 

 Arizona. 



The San Pedro river of Arizona drains a 

 considerable area, and is bordered through- 

 out its course by mountain ranges forming 

 a valley from ten to twenty miles in -width 

 and nearly one hundred and fifty miles im 

 length. The valley is in general parallel 

 with that of the Santa Cruz, the next great 

 valley to the westward. A lake-like sheet 

 of water of which we have good evidence- 

 filled the greater portion of this valley in 

 late Tertiary or Quaternary time. This; 

 OA^dence is chiefly the presence on both 

 sides of the valley of unconsolidated red 

 clays and sediments in horizontal beds of 

 great thickness, often terraced by the river- 

 erosion, and extending high up on the sides 

 of the bordering mountains. One of the 

 best cross-sections is found on the line of 

 the Southern Pacific railway which crosses 

 the valley nearly at right angles to its 

 course at Benson. Benson, in the bottom 

 of the valley, has an altitude of 3,576 feet 

 above the sea. The river is about fifty feet 

 lower. The lacustrine clays rise from this 

 point on each side to the height of about 

 3,800 feet. The exact limit of clay deposi- 

 tion is not easily determined. It appears 

 most probable that the height of the water 

 was about 4,000 feet above tide. The sedi- 

 ments are similar to those around Benson, 

 bordering the valley northwards, towards 

 the Gila Valley. We there find also, in addi- 

 tion, the thick beds of diatomite mingled 

 with fine volcanic ash. These diatoms are 

 mostly marine species, according to Dr. D. 

 B. Ward, of Poughkeepsie. But some 

 fresh Avater forms are present. The 

 Quiberis Valley thus appears to have been 

 occupied by sea-water. It was open on the 

 north to the great open valley of the Gila 

 and Salt rivers and would appear to have 

 existed as a partly landlocked estuary, at 

 least in the upper portion between the 



