186 GUIDEBOOK OF THE WESTERN UNITED STATES 
According to long observations by the United States Weather 
Bureau the average annual precipitation at Tucson is 11.8 inches, 
usually with the maximum rainfall in July. The precipitation shows 
wide variation, however, sometimes falling considerably below 10 
inches (5.26 inches in 1885) and occasionally exceeding 15 inches 
(24 inches in 1905). The mean annual temperature is 67.3, and the 
humidity is generally considerably under 50 per cent. The daily 
range in temperature ordinarily varies from 32° to 57°. The average 
number of sunshiny days in the year is 309. Snow is rare in the valley 
but often falls heavily on the surrounding high mountains. 
Tucson is built on the nearly level desert on the east bank of the 
Santa Cruz River, a wide watercourse which is dry most of the time. 
In every direction are fine views of the splendid mountains that 
encompass the far-reaching desert flat. To the north is the high 
Santa Catalina Range, which rises more than a mile above the slopes 
at its base; its highest summit, Mount Lemmon (elevation 9,150 
feet), is in plain sight. This range is continued far to the east in 
the Tanque Verde and Rincon Mountains. To the south are the 
Santa Rita Mountains and the Sierrita Range, separated by the 
valley of the Santa Cruz River, and to the west and northwest are 
the pinnacled Tucson Mountains, not high but very rugged. Beyond 
the Sierrita Mountains is a distant view of the prominent Babo- 
quivari Peak (bah-bo-kee-vah’ree). 
_ There was considerable mining in the general region about Tucson 
by Spaniards, Mexicans, and Americans down to 1861, when all 
industry ceased. It was revived in 1878 with the discovery of rich 
ores at Tombstone. Several productive mines are now in operation 
in the Empire, Santa Rita, and Sierrita Mountains. In the Twin 
Buttes, on the east side of the Sierrita Mountains, there are mines 
producing ores of silver, copper, and lead. 
The Santa Cruz River rises in Mexico south of Nogales, and on the 
rare occasions when it carries a large flood it empties into the Gila 
River southwest of Phoenix; its total length is thus about 200 miles. 
With the advent of the missionary-explorers, in the early days, its 
valley became an important artery of travel from the western part of 
Mexico to Arizona and the north and west. The first of these 
explorers of whom there is authentic record was the heroic German 
Jesuit Eusebio Francisco Kino, who spent 20 years in constant jour- 
neying, often entirely alone, throughout the Indian region as far west 
8 the Colorado River. He left Mexico City in 1687 and, after found- 
ing several missions in northern Mexico, reached the Indian rancherfas 
of Guevavi and Bac, on the Santa Cruz River, in 1691. In the 
next few years he reached the coast of the Gulf of California and also 
discovered Casa Grande, on the Gila River. He visited Mexico City in 
1695. In 1696 he reached Quiburi (kee-boo’ree), the Indian settle- 
‘ment on the San Pedro River. He visited this place again in 1697 and 
