288 NEW TRACKS IN NORTH AMERIGA. 
The San Luis valley, lying above this cafoned portion of the valley, presents — 
course of the numerous tributary streams owing down from the high moun- 
tain ridges on either side of the main valley. 
This section is particularly adapted to the growth of cereals and root crops, 
and in its cool atmosphere abundance of grass and clear flowing water is 
eminently a dairy region. 
a wide alluvial basin, including extensive tracts of fertile soil, lying along the 
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distinction in their products, the former being adapted to small grains, 
potatoes, butter, and cheese, the latter to maize and fruits. In this condition 
things, an exchange of products would prove of mutual advantage, and 
afford profitable business in the way of transportation in both directions 
forests of pifion and cedar, which occupy adjoining rocky and barren ridges, 
while the higher mountain ranges will supply lumber and building material to 
any desired extent. ae 
The lower portion of the valley of the Rio Grande includes the district 
generally referred to as New Mexi 
wide alluvial or sandy bottoms, bounded by bluffs of grayel and occasional 
rocky declivities, capped with basalt. The flora here includes the plants 
referred to in the accompanying list as New Mexican, Owing to the more 
moderate in extent, and occurring at the proper season, help to main 8 
natural fertility of the soil, but are occasionally very destructive ) 
growing crops, or un ing and transporting large tracts of fertile soil, 
unding, with abrupt mural faces, y eys of erosion; th ta are 
interrupted at various points by igneous protrusions and overflows of basalt 
and lava, serving versify in a remarkab external features of 
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scenery, and to modify the texture and composition of the overlying soil. is 
especially noticeable in the character of the native yegetation, which is directly 
ted to these variable conditions. Thus, on the dry uplands and mesas, we 
end watered growth of grama, interrupted with occasional growths of cedar 
_ and pifton. On the more elevated mountain ridges we meet with dense 
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