H. J. Biddle — Surface Geology of Southern Oregon. 477 



Next to be considered is the region embraced in the valleys 

 of Summer, Abert and Goose lakes. While each of these lakes 

 has its own system of drainage, all being at present without 

 outlet, yet from the fact that they are only separated by divides 

 of slight elevation in comparison to the surrounding mountains, 

 they can conveniently be grouped together. Another reason 

 for considering them together is, as will be shown, the proba- 

 bility that they once belonged to the same drainage system. 



The valleys of Summer and Abert lakes, together with the 

 low region between them, now occupied by the Chewaucan 

 Marsh, were filled, during the Quaternary period, by a lake of 

 considerable size. The boundaries of this ancient lake have 

 been mapped by .Russell.* In the lowest portions of its bed 

 are the existing lakes, Summer and Abert. They resemble 

 each other in many respects, and are both highly charged 

 with various salts in solution ; but the waters of Abert lake 

 contain about twice as great a percentage of total solids as 

 those of Summer lake. Qualitatively the salts in both lakes 

 are the same. A sample of the water of Abert lake was col- 

 lected on the 18th of September, 1887, off a rocky point near 

 the middle of the west shore. It was taken one foot below 

 the surface and about ten yards from land ; the depth of the 

 water being five feet, and temperature 15° C. The following 

 analysis of this sample by Dr. T. M. Chatard, of the U. S. 

 Geological Survey, is published by permission. 



Specific Gravity 1-03117 at 19-8°. 



In 25 c.c. =25'77295 grams. Grains in Percentage 



A. B. Average. a liter. of total solids. 



Sid„ 0-0063 0-0053 0*00580 0'232 0-59 



K 0-0133 0-0136 0-O1345 0-538 1*37 



Na 0-2674 0-3671 0-36725 14-690 37*51 



S0 3 } 0-0148 0-0146 0-01470 0*5*8 1-50 



O \ U-0030 0-0029 0-00295 0"U8 0'30 



CI 0-3365 0-3366 0-33655 13-462 34-37 



C0 2 ) 0-1755 0-1757 0-17560 7*024 17*93 



O j" 0-0615 0-0616 0-06155 2"462 6-28 



H in bicarbonates 0*058 0-15 



Grams 39-172 100*00 



Hypothetical Composition. 



Grams in a liter. Percentage of total solids. 



Si0 2 0*232 0-59 



KC1 1-027 2-62 



NaCl . 21-380 54-58 



Na 2 SG 4 1-050 2-68 



Na 2 C0 3 10-611 27-09 



NaHCO. 4-872 12-44 



39-172 100-00 



* Loc. cit., map 83. 



