ORIGIN OF LAKE BASINS. 21 



streams of hardened lava extend outward towards the great walls enclosing 

 the lake, but do not n-ach tlieni. 



The sounding line has shown that Crater lake has a maximum depth 

 of 2000 feet and is the deepest lake now known in North America ; its 

 nearest rival ])eing Lake Tahoe. The full depth of the l)asin measured 

 from the erest of the enclosing cliff's, is from 2900 to 4200 feet. 



The rugged slopes encircling the lake as well as the island that seem- 

 ingly floats on its placid surface, are forest covered, thus softening and 

 rendering pictures(pie the otherwise oi)pressive grandeur of the scene. 



More remarkable, however, than the unicjue scenic features of Crater 

 lake, is the story of its origin. The site of the great depression was once 

 occupied by a volcanic mountain which reached far above the highest 

 j)oint on the cliffs now enclosing it. and was proljal^ly as conspicuous a 

 member of the sisterhood of mountains of which it formed a part, as any 

 of the neigliboring peaks, but the once prominent pile has been removed 

 so as to leave the profound gulf that now fascinates and startles tlie 

 ol)server. The cliaracter of the sculpturing on the outer slope of the 

 truncated mountain shows that it was eroded, both by streams and by 

 glaciers, before the catastrophe that carried away its summit and left only 

 a hollow stum[) to mark the site of the ice-crowned peak that formerly 

 gleamed in the sky. 



The removal of the summit of the mountain is su])})0sed to have been 

 due to a mighty ex})losion, similar to that uhich l)lew off" 5000 feet from 

 Kiakatoa ; or else that the mountain was melted from Avithin and its 

 summit engulfed so as to leave the depression now partially filled with 

 l)lacid waters. Of these two hypotheses, the second seems to accord best 

 w ith the observed facts, for the reason that fragmental deposits on the 

 surface of the adjacent country, of the character that would be expected 

 had the summit of the mountain Ijeen blown away, have not been recog- 

 nized. Subsequent to the removal of the summit of the mountain, 

 renewed volcanic energy of a mild character Ijuilt the crater-island within 

 the crater-ring. 



A circular depression in l)ut little disturlied stratified rocks which 

 bears some resemblance to a crater-ring, and which seems likely to fumish 

 the key to the origin of tlie calderas of Italy ami other regions, has 

 recently Ijeen discovered in Arizona, a1)()ut 25 miles southeast of the 

 town of Flagstaff, This unicjue basin has been carefully studied by 

 (J. K. (iilbert, but no account of it from his pen has come under tlie 

 writei-'s notice. Tiie ol)servations stated below are main]\- finni a 



