110 E. L. Berthoud—McChllan Mountain, Colorado. 



three-fourths of a mile distant and upon another high peak, the 

 limit of tree growth exceeds 12,400 feet elevation on the south 

 slope of that peak. Here can be seen Pinus aristaia, some of the 

 trees two feet in diameter and thirty feet high that retain their 

 hold, and slowly increase in size, thus maintaining themselves in 

 respectable numbers in spite of furious gales of snow and wind, 

 and an extreme Arctic cold. 



In Miscellaneous Publications, No. 1, U. S. Geological Sur- 

 vey of the Territories, which was published last year, under the 

 direction of Prof. F. V. Hayden, the line of tree growth is given 

 by Mr. J. T. Gardner in his report, as from 11,000 feet to 11,900 

 feet, between latitudes 39° and 40°. We believe this to be cor- 

 rect, and a fair general average. In Argentine District, which 

 comprises McClellan Mountain, we have a very notable depart- 

 ure from this limit of from 500 to 1400 feet 'in elevation, and 

 also about 1300 feet above timber line on Gray's Peak, three to 

 four miles southwest, as given by Mr. Gardner. At the Equator 

 and in the Torrid zone the limit of the growth of Pines is gener- 

 ally placed at 12,800 feet above the sea ; how is it that, in lat. 

 39° 33' K, the limit of the growth of Pines has receded only 400 

 feet? 



In McClellan Mountain and in Argentine District there are 

 two antagonistic phenomena in immediate proximity ; on one 

 side of the valley, a mountain slope facing north east, well grassed, 

 totally devoid of shrubs and trees, where soil and rocky debris 

 are underlain by a perpetual icy coat of hundreds of feet in depth, 

 supporting on its surface a growth of plants strictly Alpine and 

 Arctic, and abounding with Ptarmigan, Lagopm leucurus, and 

 the tailless, earless marmot ; and where on the 2d October, 1876, 

 I found the following plants yet in bloom; Sedum stenopetahm, 

 Poi^idilla norvegica, P.fruticosa, ^Sibbaldia procumbens. Astragalus 

 alpitms, Silene ucatdis, Draba aurea, Pkleam alpinum, Primula 

 Parry i, Gentiana, I/eucha-a, Cast die la pallida, Ranunculus invalis, 

 Peaicularis, Cardamine and Crepis, while less than half mile dis- 

 tant, on the opposite slope of the vale, Pimis aristata of large size 

 and a profuse growth of birches, willows, grasses and Arbutus, 

 with flowing springs and small ponds, diversify its southwestern 

 slope. 



It has been suggested* that the frozen soil and rock of some 

 mines examined by him, northwest from McClellan Mountain, on 

 the west slope, have been thus left ice bound since the Glacial 

 period ; and that they thus retain their former ice-bound condi- 

 tion, from the excessive altitude of the mines there explored. 



This may be the case, but it seems doubtful. There are in Col- 

 orado many mines at altitudes very nearly as high as the highest 

 on McClellan Mountain, yet none have been exploited to the 

 * R. Weiaer, in this Journal, III, viii, 477, 1874. 



