ENGELMANN — ALTITUDE OF PIKE'S PEAK. 129 



high peaks with the St. Louis station gave a somewhat differ- 

 ent result, making them mostly from from 80 to 100 ft. lower. 



I have for the computation made use of Delcros' Tables as 

 prepared by Prof. Guyot and published by the Smithsonian 

 Institution. 



An important and curious, though not quite unexpected, 

 result of Dr. Parry's measurements is the discovery, that the 

 limit of arborescent vegetation is, in Colorado, reached only 

 at an altitude of between 11,600 and 12,000 feet ; an elevation 

 which nearly corresponds with the same limit in the great 

 mountain ranges of the globe nearer to the equator. Thus 

 the Schlagintweits give the limit of the trees on the Hima- 

 laya (about lat. 31°) at 11,800 ft.; on the Andes within the 

 tropics it is said by Humboldt not to reach over between 

 11,000 and 1*2,000 feet ; only in Mexico do I find it recorded as 

 high as 12,800 feet. On the mountains of the same or even 

 lower latitudes it is much lower than in Colorado ; thus on 

 the Peak of Teneriffe (lat. 28°) it reaches only to 7,300 feet; 

 on Mt. Etna (lat. 38°, nearly the same as Pike's Peak) to 

 6,G00 feet, and in the Alps of Switzerland (about lat. 40°) on 

 an average also to 6,500 feet. The cause of this remarkable 

 apparent deviation from physical laws is to be found in the 

 great elevation of the greatest plateau on the globe, which 

 extends between the upper confluents of the Mississippi and 

 the California coast range over from 12 to 20 degrees of lon- 

 gitude, and from the plateau of Mexico far into the British 

 possessions, widest between the parallels of 40 and 42 de- 

 grees, at an elevation of between 4,000 to 7,000 feet, reaching 

 its highest points just in Colorado Territory,* carrying the 

 general mean temperature of the whole region far above that 

 of smaller mountain ranges or isolated peaks of the same alti- 

 tude and under the same latitude. 



Another cause of this higher mean temperature will be found 

 in the absence of large masses of perpetual snow in the Colora- 

 do mountains, which, whenever present, cannot fail to depress 

 the temperature of the regions next below them. The snow- 

 line proper is not reached in the Colorado mountains at all, 

 though masses of snow are found on many high points all the 

 year round. The only chain of the Rocky Mountains proper 

 supposed to reach into the limits of perpetual snow are the 

 Wind River mountains (lat. 42°), where, according to Fre- 

 mont's observations, made in Aug., 1842, the arborescent vege- 

 ation attains its upper limit at 10,160 feet (1,500 to 1,800 ft. 

 lower than in Colorado), and the snow-line commences about 



* Dr. Parry is confident that a number of peaks, not yet explored, 

 reach quite up to 15,0(10 feet or more; so tha^ the palm lately awarded 

 by Prof. T. D. Whitney to Mt. Shasta in California (14,410 feer) as the 

 high-st point in the territory of the United States, may soon have to be 

 transferred to some peak in Colorado. 



9 



