74 CARNEGIE INSTITUTION 



from the summit. Their slopes are practically unscalable except De- 

 constructed trails. Where the steepness does not forbid the way, the 

 chaparral everywhere disputes it. This brushwood growth is pecu- 

 liarly characteristic of the semi-arid mountains of southern Califor- 

 nia. Mount Lowe wears this covering of chaparral, but it is no- 

 where luxuriant. The decomposing white granite is inhospitable 

 soil for vegetable growth. The mountain is sterile and forbidding, 

 except in a few of its canyons. The white granite sand, scarcely 

 covered at all with accumulating humus, stares everywhere through 

 the irregular lanes in the chaparral. In many places the faces of the 

 slopes lie almost bare and glitter unpleasantly in the sun. There is 

 little doubt that radiation from the exposed surfaces accounts for the 

 fact that the day seeing both at Echo mountain and at the higher 

 station at Inspiration point averaged lower than the night seeing, 

 which was, on the whole, excellent. 



The term mesa is used in the Southwest to denote the fringe of 

 detritus washed down from the mountains and sloping away from 

 their bases to the plains, or the mesa may be formed, as in the region 

 about Flagstaff, Arizona, by lava flows from volcanic cones ; but 

 always, if one examines it as a whole, one finds a sloping upland 

 contiguous on the upper side to mountains and on the lower side to 

 plains or valleys. It is in this sense of contiguous sloping uplands 

 that I use the word in this report. 



My departure from L,os Angeles for the south was somewhat de- 

 layed by the accidental side-tracking of a part of the freight in its 

 shipment down from Echo mountain. In the meantime I made my 

 first trip to Mount Wilson, going up the Sierra Madre trail on the 

 east side, staying over night, and descending the west or Pasadena 

 trail on the second afternoon. Some days previously I had the good 

 fortune to make the acquaintance of Mr. T. P. L,ukens, of the 

 United States Forestry Commission. He has been of the greatest 

 assistance to me in furnishing reliable information respecting the 

 mountains of southern California and northern Arizona. He spoke 

 enthusiastically of Mount Wilson and advised me to see it. The only 

 access to this peak at present is by the trails just mentioned. These 

 are only wide enough for pack animals, burros, or mules, and about 

 four hours is required for the ascent or descent. I had been assured 

 that Mount Wilson was very different from Mount Eowe, though 

 from the valley it has the same grim outlines; but I was quite un- 

 prepared for the actual view of it. Instead of one barren rock, a 

 succession of rolling knolls forms the summit. The canyons con- 



