Geology of Ft. Apache Region, Ariz. — Reagan. 303 
-total decomposition of the limestone particles, but the heat impartd to 
them a crystalline structure; hence the 'calcite' in the amygdaloid 
spaces.'' 
The age of these lavas is undoubtedly late Quaternary 
because they overlie the Quaternary of the Plateau and under- 
lie the Post-glacial. 
Economics. Climate. 
The tablelands and mountains of this region are cool in 
summer but the climate is not severe in winter. The valleys 
and lowlands are very hot, frost being seldorh seen in the 
Salt river and Globe districts. The country as a whole is 
arid, the precipitation at Fort Apache in 1900 being but 
twenty inches, and crops are raised only by irrigation. 
Soil. 
The soil is not deep but is fairly fertile even on the table 
lands. In the valleys, where irrigated, crops do well, and 
on the table lands are filaree and grama grasses and forests. 
An analysis by Mr. Loew of the soil on the Mogollon 
rmgc resulted as follows: 
Physical condition: Color, dark; consistency, loose. 
Per cent. 
Sand 42.20 
Silt and clay 37-98 
Hydroscopic moisture 10.98 
Humus and chemically-bound water 8.84 
Chemical Constituents* 
Pota ssa 0.115 
T So t ? a ( Traces 
Lithia ) 
Magnesia 029 
Lime .. 0.153 
Phosphoric acid 0.058 
Oxide of iron ) 
Alumina V by diff 2.013 
Sulphuric acid ) 
Total soluble in hydrochloric acid, water included 22.188 
Insoluble quartz and clay 77-8i2 
100 
Vegetation. 
This region may be divided into four distinct plant zones 
( iccoiding to altitude) : 
1. — This zone includes all the lands of the region above 
5800 feet. It is well timbered, the principal trees being pine 
ami fir. 
