32 



SCIENCE 



[N. S. Vol. XXXI. No. 784 



Bancroft was a physician, who resided on 

 the river Demerara, from which he wrote let- 

 ters to his brother under dates July S-Novem- 

 ber 15, 1766. In 1769, these letters were col- 

 lected and published in a volume, under the 

 above title, dedicated to William Pitcairn, 

 M.D., fellow of the Royal College of Physi- 

 cians in London and Physician of St. Bar- 

 tholomew's Hospital. The copy from which 

 this extract is taken may be found in the 

 Library of Congress at Washington. 



E. W. GUDGER 



State Noemal College, 

 Geeensbobo, N. C. 



SPECIAL ARTICLES 



GLACIATIOISr IN THE SAN BERNARDINO RANGE, 

 CALIFORNIA 



While engaged in the study of the moun- 

 tains of southern California the past summer 

 the writers spent a week about the slopes of 

 San Gorgonio Mountain, the highest point of 

 the San Bernardino range. The important 

 discovery was made of unmistakable signs of 

 former glaciation upon its northern' slope. 

 This is a fact of considerable interest because 

 it has hitherto been assumed that the south- 

 ernmost point of glaciation in the United 

 States was in the Sierra Nevadas, nearly two 

 hundred miles to the north. 



The San Bernardino range is topographic- 

 ally distinct from any other mountains of 

 southern California. It appears to be much 

 younger than the San Gabriel range, from 

 which it is separated by the Cajon Pass, and 

 also to have had a different history from the 

 San Jacinto Mountains, which lie to the south 

 on the opposite side of the San Gorgonio pass. 



The topography of the range is marked by 

 broad elevated valleys, and plateau-like ridges. 

 There are several undrained basins quite sim- 

 ilar to those in the desert immediately ad- 

 joining on the north, and it seems reasonable 

 to assume that the range as a whole is an up- 

 lifted fault block of what was once topograph- 

 ically a portion of the Mohave desert. 



The highest portion of the range forms a 

 rather sharp ridge about six miles long and 



extending a little north of west and south of 

 east. San Bernardino Mountain forms the 

 western end of this ridge with an elevation of 

 10,630 feet, while the eastern end is known as 

 San Gorgonio Mountain with a height of 

 11,485 feet. The Santa Ana River, the main 

 stream in the range, drains the northern 

 slope of this ridge, receiving its large perma- 

 nent flow of cold water from the glacial 

 gravels and the snow banks which linger late 

 in the season in the heads of the protected 

 canons. 



The largest glacier existed on the north- 

 west slope of San Gorgonio in a semicircular 

 basin made by a northerly curve of the ridge 

 running westerly to San Bernardino Moun- 

 tain. Here is a true glacial cirque, and from 

 its margins well-characterized morainal ridges 

 extend downward for about a mile into the 

 basin of the South Fork of the Santa Ana 

 River, and block a small tributary from the 

 east. Above the dam thus made is a body of 

 water about a quarter of a mile across known 

 as Dry Lake. The lower marginal moraine 

 reached fully three quarters of a mile below 

 the lake, the total width of the glacier at its 

 lower end being indicated by this distance. 

 The rock debris on its lower side forms a great 

 wall across the valley 300 to 400 feet high. 

 The glacier appears to have been overloaded 

 with debris and after having first reached the 

 lowest point where there is a great quantity of 

 partly modified morainal material, to have 

 been crowded progressively eastward back 

 toward the present Dry Lake. In places two 

 to three marginal moraines appear and several 

 basin-like depressions resembling kettle holes. 

 No bedrock is visible in the. path of the 

 glacier and scratched boulders were not recog- 

 nized with certainty. The granitic rocks are 

 coarse and crumble rapidly and it is not to be 

 wondered at that no boulders thus marked 

 were seen. Great springs issue from the 

 lower margin of these glacial gravels, form- 

 ing a typical mountain meadow with abun- 

 dance of grass and a cool bracing air. 



Another typical cirque basin lies close up 

 under the northeast crest of San Gorgonio, 

 and contains snow drifts nearly all summer. 



