276 Rear. 3 Gannett-—The “Timber Line.” 
Therefore, in considering the height of the timber line, we 
must regard the mountain ranges in connection with the plateaus 
upon which they stand, their latitudes, heights and masses, or 
what, in a measure, sums up these three, their temperatures, as 
it is by these that its height is determined. 
Looking at the subject from this point of view, a fair com- 
parison may be instituted between the timber line in different 
latitudes and on different ranges in the same latitude. 
The actual elevation above sea level of the timber line in the 
Cordilleras of North America ranges from 6 or 7,000 to 12,000 
feet. It is lowest in the Coast and Cascade Ranges of Wash- 
ington Territory, where it is at about the former figures. Fol- 
lowing the Cascade Range southward into Oregon, the timber 
line rises to a height of 7,000 to 8,000 feet. It continues to 
increase as we trace it southward into California, being on 
Shasta and the neighboring mountains 8,000 feet above the sea. 
On the high sierras of Hastern-central California, forests grow 
to 10,000 or 11,000 feet, while the San Bernardino and other 
ranges of Southern California do not reach the upper limit of 
forests. 
Few of the ranges of Nevada reach the timber line, which is 
at a height of 9,000 feet in the north up to, probably, 11,000 
feet in the southern part of the State. : 
In Arizona, probably none of the mountains reach the timber 
line, except the voleanic group known as the San Francisco 
Mountains, and the Sierra Blanca. On these the timber line is 
between 11,000 and 12,000 feet. 
In New Mexico, it averages about 12,000 feet above sea 
level. There is little variation between the northern and 
southern parts of the territory, as the higher annual tempera- 
ture of the southern part is fully compensated for by the greater 
Colorado, it ranges from 12,000 feet in the ssc 
e 
San Juan Mountains and in the Sangre de Cristo range, and 
In Montana and Idaho, the limit of timber is, in general, from 
9,000 to 10,000 feet, being highest in the south, and lowest near 
the northern boundary. ° ey 
In the Uinta and Wahsatch Ranges of Utah, it 1s about 
11,000 feet, rising somewhat above this figure in the southern 
part of the latter range. 
