130 TRANS. OF THE ACAD. OF SCIENCE. 



feet higher, with 12,400 feet, while the summit of Fremont's 

 Peak reaches more than 1,100 feet into the region of eternal 

 winter, to 13,570 feet. 



Besides this, I find in the works at my disposal only the 

 following notices about the altitude of the upper tree limits 

 in our western mountains : 



Capt. Gunnison states (Pacif. R. Rep. 2, p. 47), that pines 

 and aspen groves occur on the mountain sides over the Co- 

 chatoopee Pass (lat. 38°), which itself is 10,000 feet high. 



Capt. Whipple (ib. 4, p. 20) tells us, that Pinus flexilis is 

 found on the Sandia Mountains, in eastern New Mexico (lat. 

 35°), at an elevation of 12,000 feet, and Dr. Bigelow, who as- 

 cended these mountains, informs me that their top is covered 

 with that pine. Capt. Whipple further states (ib. Appendix, 

 p. 280, note) that on the San Francisco Mountain, in western 

 New Mexico, in the same latitude, the pine timber reaches 

 up to 504 feet of the summit of 12,052 feet; therefore, to an 

 elevation of 11,548 feet. In another place (vol. 3, Geol., p. 7) 

 the summit is stated to be 13,000 feet high, which, if correct, 

 would bring the upper limit of trees to about 12,500 feet. 



My brother, Henry Engelmann, informs me, that in Capt. 

 Simpson's expedition he found the highest growth of trees on 

 the level, wet tops of the Uintah Mountains (lat. 41°), south 

 of Fort Bridger, to consist of aspen, at 10,000 feet elevation ; 

 and that in August he met with snow there on the same level. 



Corresponding with this observation, Dr. Newberry (Pac. 

 R. Rep. 6, Bot., p. 44) found the line of "perpetual" snow on 

 the Cascade Mountains, in lat. 44°, at 7,000 feet; at 6,500 feet 

 he found good sized pine timber, and higher up, "to the snow- 

 line itself," pines of scrubby growth. Both these observations 

 cannot refer to a real snow-line, as that never reaches down 

 to the limit even of the most scrubby pines.* 



As everywhere else in the northern hemisphere, or rather 

 north of the tropics, Coniferse are in Colorado those trees 

 which form the extreme limit of arborescent vegetation, 

 though aspen and birches reach almost as high in suitable, 

 moist localities. 



The following tables exhibit some interesting facts in rela- 

 tion to the distribution of the incipient population of Colo- 

 rado over different altitudes. The "cities" extend from 5,300 

 feet (Denver) to 8,600 feet (Empire City), and a few small 

 towns even reach to near 10,000 feet (Jefferson and Tarryall). 

 Ranches — i. e., farms, the upper ones only grazing farms — are 

 found up to about the same elevation. Dr. Parry, however, 

 informs me, that crops of wheat, maize, barley, oats, &c, are 



• Mount Washington, in New Hampshire (lat. 44°), 6,285 feet high, 

 does not reacli to the snow-line, but the timber ceases at perhaps 1,000 

 feet below the top, say at 5,000 or 5,200 feet altitude. 



