Apbil 10, 1008] 



SCIENCE 



585 



valuable as a source of general information 

 on the subject. 



Inez Whipple Wilder 

 Smith Coixege, 

 Northampton, Mass. 



SOCIETIES AND ACADEMIES 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



At the 201st meeting of the society, held in 

 the Cosmos Club, on Wednesday evening, Feb- 

 ruary 26, the following papers were presented : 



Regular Program 

 Evidences of Recent Volcanic Activity and 



the Glaciers of Mt. Hood, Oregon: A. H. 



Sylvester. 



Mt. Hood, the highest mountain in Oregon 

 and one of the most beautiful of the ice-cov- 

 ered extinct volcanoes of the Cascade Range, 

 lies on the crest of that range about 20 miles 

 south of the Columbia Eiver. Its elevation 

 is 11,225 feet. About two thirds of its crater 

 remains, the southwest side being broken away. 



The evidence of field observations and the 

 new topographic map made by the writer last 

 summer point to a very extensive glaciation 

 at some former period, and to another less 

 extensive advance in comparatively recent 

 times. 



An enormous mass of morainal material 

 covers the southwest flanks of the mountain 

 and nearly fills three of its large canyons. 

 This was probably derived from the cutting 

 away of the crater by the early glaciation. 

 The Zigzag and White River glaciers now 

 head against the inside of the north wall. 

 They have cut away the old crater floor and 

 exposed the volcanic neck or plug which now 

 stands a prominent feature in the center of 

 the ruined crater and is known as Crater 

 Rock. 



A section exposed in White River Canyon 

 by the cutting of the present streams through 

 the morainal filling shows two layers of drift 

 separated by a layer of soil and logs in place, 

 and ten or twenty feet of fossil ice under- 

 lying all. There are eight glaciers of fair 

 size on the mountain. On the whole, they are 

 probably receding, but owing to several recent 



heavy winters there now appears to be an 

 advance. 



The Zigzag and White River glaciers are 

 exceptions to this rule, because of volcanic 

 heat. Their lower ends are disintegrating 

 and opposite Crater Rock, the point of great- 

 est volcanic activity, the Zigzag is partially 

 and the White River wholly cut in two. 



On August 28, 1907, in addition to the usual 

 steam, smoke was seen issuing from Crater 

 Rock and at night a glow was observed. The 

 next day the White River was trebled in vol- 

 ume without other warrant than the moun- 

 tain's internal heat. 



No alarming symptoms have been observed 

 since. 



Physical Features of Peru: Geo. I. Adams. 



Peru is generally considered as containing 

 three regions: the coast, the sierra and the 

 montafia or forest. These regions differ cli- 

 matically, the coast is arid and agriculture is 

 carried on by means of irrigation. The sierra 

 has a moderate rainfall and being an elevated 

 region evaporation is great, so that the climate 

 is semi-arid. The forest region has a heavy 

 rainfall and is covered with a tropical forest. 



The coast region is a narrow belt. In the 

 northern, south-central and southern portions 

 there are coastal plains. The extent of these 

 plains was shown for the first time on the 

 maps accompanying Mr. Adams's reports of 

 his recoimaissance of the coast, published as 

 bulletins of the Corps of Engineers of Mines 

 of Peru. Between the northern and south- 

 central plains and likewise between the south- 

 central and southern plains the mountains 

 descend to the sea. Between the southern 

 plains and the sea there is a range of coast 

 hills. The coastal plains are occupied by 

 Tertiary formations. 



The division between coast and sierra is 

 dependent upon elevation, not upon topog- 

 raphy, and corresponds with the limit of gen- 

 eral annual rainfall excepting to the north- 

 ward, where the rainfaU extends over a por- 

 tion of the coastal plains in the region of the 

 GuK of Guayaquil. The approximate limit 

 of the annual rainfall is shown on Mr. Adams's 



