GAZETTEER OF COLORADO. 
Elevations in < 'olorado. 
From— 
Square 
miles. 
From— 
Square 
miles. 
3 000 to 4,000 feet 
4,900 
22,700 ' 
17,100 
12,725 
7,000 to 8,000 feet 
13,500 
4 000 to 5 000 feel 
8,000 to 9,000 feet 
11,500 
5 000 to 6 000 feet 
9,000 to 10,000 feet 
8,600 
6,000 to 7,000 feet 
Above 10,000 feet 
12, 900 
The principal rivers are North Platte, South Platte, Arkansas, Ki<> Grande, Yampa, 
White, Grand, Gunnison, Dolores, and San Juan. None of these streams are navigable. 
They head in the mountains, and with steep and rugged courses flow to the plains or 
plateaus. These rivers, with their numerous branches in the mountain country of 
Colorado, probably furnish a more abundant supply of water for irrigation purposes 
than the streams of any other State in the arid region. Most of them are drawn 
upon heavily in aid of irrigation. 
CLIMATE. 
Although Colorado is greatly elevated above sea level, the lowest portion along the 
east boundary being 3,000 feet in altitude, the temperature is but slightly lower than 
in regions of the same latitude near sea level, because the isothermal lines are carried 
up by the great mass of country. The mean annual temperature of the plains and 
plateaus ranges from 45° to 55°, while that of the higher mountain valleys or parks 
is 40° or even less, and upon the mountain ranges it is still lower. 
The range of temperature between day and night, between summer and winter, 
and between the highest and lowest temperatures recorded, is very great, far greater 
than in the Mississippi Valley or on the Atlantic coast. Thus the difference between 
the temperatures of the coldest and warmest months is, on an average, not far from 
50°. Upon the plains, at such points as Denver and Colorado Springs, the tempera- 
ture frequently falls below zero in winter, while summer temperatures above 100° 
are often recorded, and on the low plateaus in the western part the range of tem- 
perature is even greater. 
Colorado lies within the arid region. The plains to the east of the mountains and 
the plateaus to the west have an annual rainfall of less than 20 inches, decreasing in 
some localities, especially in the western part, to 10 inches or even less. In the 
mountains the rainfall is greater, exceeding 30 inches. The distribution of rainfall 
throughout the year is peculiar to the Rocky Mountain region; instead of falling 
mainly in the winter time, as is the case on the Pacific coast, the summer is the 
rainy season, and instead of long storms the rain comes in the form of showers. At 
Denver five-sixths of the annual precipitation falls from May to October, inclusive, 
and in other parts of the State the proportion in these months is from two-thirds to 
nine-tenths of the total annual precipitation. The cause of this phenomenon is that 
in winter the ranges bordering the Pacific (this ocean being the source of precipitation 
for the entire western country) take practically all the moisture from the vapor-laden 
winds coming off that ocean, while in summer, owing to the fact that these ranges 
are relatively warmer, a part of the moisture is carried over to the interior country. 
The aridity of the region is shown not only in the light rainfall, but in the relative 
humidity of the atmosphere. On the plains and plateaus the average relative 
i humidity is not far from 50 per cent — that is, the air contains on an average only 
about one-half the moisture which it is possible for it to absorb. 
