MINDELEFF] ENVIRONMENTAL INFLUENCES 481 
to the other conditions and enables him to lead a life which is on the 
whole not onerous. 
In these dry elevated regions the heat is never oppressive in the 
day and the nights are always cool. Day temperatures of 120° or 
more are not uncommon in the valleys in July and August, but the 
humidity is so slight that such high readings do not produce the dis- 
comfort the figures might imply. In his calico shirt and breeches the 
Navaho is quite comfortable, and in the cool of the evening and night 
he has but to add a blanket, which he always has within reach. The 
range between the day and night temperature in summer is often very 
great, but the houses are constructed to meet these conditions; they 
are cool in hot weather and warm in cold weather. 
The extreme dryness of the air has another advantage from the 
Indian point of view, in that it permits a certain degree of filthiness. 
This seems inseparable from the Indian character, but it would be 
impossible in a moist climate; even under the favorable conditions of 
the plateau country many of the tribes are periodically decimated by 
smallpox. 
HABITS OF THE PEOPLE 
The habits of a people, which are to a certain extent the product of 
the country in which they live, in turn have a pronounced effect on their 
habitations. New Mexico and Arizona came into the possession of the 
United States in 1846, and prior to that time the Navaho lived chiefly 
by war and plunder. The Mexican settlers along the Rio Grande and 
the Pueblo Indians of the same region were the principal contributors 
to their welfare, and the thousands of sheep and horses which were 
stolen from these people formed the nucleus or starting point of the 
large flocks and herds which constitute the wealth of the Navaho 
today. 
The Navaho reservation is better suited tor the raising of sheep than 
for anything else, and the step from the life of a warrior and hunter to 
that of a shepherd is not a long one, nor a hard one to take. Under 
the stress of necessity the Navaho became a peaceable pastoral tribe, 
living by their flocks and herds, and practicing horticulture only in an 
extremely limited and precarious way. Under modern conditions they 
are Slowly developing into an agricultural tribe, and this development 
has already progressed far enough to materially affect their house 
structures; butin a general way it may be said that they are a pastoral 
people, and their habits have been dictated largely by that mode of life. 
Hyvery family is possessed of a flock of sheep and goats, sometimes 
numbering many thousands, and a band of horses, generally several 
hundreds, in a few instances several thousands. In recent times many 
possess small herds of cattle, the progeny of those which strayed into 
the reservation from the numerous large herds in its vicinity, or were 
picked up about the borders by some Navaho whose thrift was more 
17 ETH, Pr. 2 2 
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