574 ADAPTATION OF THE COUNTRY 
So with the great California desert west of the Colorado ; 
all routes south of the 36th parallel must cross this, even 
though the Mohavi River be followed, unless the explorations 
now being made should discover some valley or stream not yet 
known. 
Some observations are necessary respecting timber and 
other materials requisite for the construction of a railway. 
Forests and timbered lands extend from the basin of the Mis- 
sissippi through eastern Texas, and on the slopes leading to 
the table-land, where they are limited to the margin of the 
streams. The next are found in the Guadalupe range of 
mountains, as well as in defiles leading to it, or following a more 
northerly line, in the Sacramento range. Both pine and oak 
exist here in abundance. Next, we have the open plains to 
the Organ Mountains, a chain running north and south about 
fifteen miles east of the RioGrande. Here both oak and pine 
timber are found. Proceeding west across the Rio Grande, the 
supply of timber must be obtained from the Rocky Mountainsin 
the vicinity of the Copper Mines (FortWebster). Beyond this, 
north of the 32d parallel, there are no elevated mountains, and 
hence no pines. The mountain defiles are filled with oaks of a 
small size, and the margin of arroyos and streams with cotton- 
woods. In the valley of the Santa Cruz, between Tubac and San- 
ta Cruz, are very considerable forests of mezquit, the best mate- 
rial for rail-ties that can be found. Next to this is the valley 
of the Gila, which is only wooded at intervals with cotton- 
woods and mezquit. For portions of the distance, the use of 
stone for sleepers or ties, would no doubt be advisable. This 
material exists in most of the mountains ; and occasionally iso- 
_ lated rocky masses, or “buttes,” rise up suddenly from the 
plain. 
I have suggested to civil engineers the use of the roots of 
the mezquit for sleepers. These roots, even when mere shrubs, 
areas solid and compact as lignum vite, and sometimes ¢con- 
tain as much wood asa tree of twenty-five feet in height. If 
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