230 CALIFORNIA ACADEMY OF SCIENCES. 



height of the summit of Mt. Pitt, above the camp, was then 

 determined by taking readings at those two points with the same 

 barometer, the readings on the summit being taken four hours 

 after those at the camp. The atmospheric pressure in that cli- 

 mate is so constant that much more accurate results are obtain- 

 able, notwithstanding the longitudinal distance apart of the two 

 stations, than would otherwise be the case. Referring the read- 

 ings taken on the summit of Mt. Pitt directly to the synchronous 

 readings taken at Portland, and calculating the elevation from 

 them, a result was obtained varying from the one given above 

 by only twenty-six feet, although the readings on the summit 

 were taken a fortnight after those from which the elevation of 

 the camp on Four Mile Lake was determined. 



The outline of Mt. Pitt, as seen from almost all sides, is that 

 of a perfect cone, and with the exception, perhaps, of Mt. Hood, 

 as seen from one or two points, it is the most symmetrical of all 

 the extinct volcanoes of the Cascade Range. It rises up out of 

 the range, and the individuality of its lower portion is lost in 

 that of the range which runs to the north and the south of it, 

 except on the west flank, which reaches to the plain. Above 

 this point, locally known as Rancherie Prairie, it rises to a height 

 of about 6,835 feet. On the south it descends only to an eleva- 

 tion of 4,988 feet, in the neighborhood of a point known as Lost 

 Prairie; while on the north it surmounts the main range by only 

 3,857 feet. Four Mile Lake, which is on the summit of the 

 Cascades, and directly at its foot, having an elevation of 5,806 

 feet. The whole southern half of the mountain, from the sum- 

 mit downwards, extending around from the east to the west, is 

 a steep unbroken slope of debris and detritus, varying in size 

 from large boulders to fine sand, with here and there a protruding 

 mass of lava, the remains of some former current not yet fully 

 disintegrated. The slope is generally very steep, and in some 

 parts attains an angle of 35°. 



On the northeast are the remains of a large crater which forms 

 a great basin-like depression on the side of the mountain. 

 Rather more than half of the wall, which includes the present 

 summit of Mt. Pitt itself, still remains. The edge of the wall 

 sweeps down from the summit in a beautiful curve almost a 



