



of Oregon and Upper California. 391 



mento and Joaquin intrude ; and it is this intermediate position 

 which gives to the region its remarkable salubrity and exuber- 

 ance of fertility. The mists and rains are collected by the high 

 ridges that bound it on the east, and at the same time a shore range 

 cuts off the cold of the coast. 



The climate of the inner portion of the Western section of the 

 territory is farther modified by the summits covered with snows 

 that occur along the Cascade mountains of Oregon, and that 

 constitute the lofty Sierra Nevada. They cause cool nights to 

 follow the hot days and ameliorate the excessive heat, especially 

 on the plains in the vicinity of the range. Within thirty miles 

 of the Shasty Peak, we had 90° F. in the shade at noon, and 

 32° P. the next morning just before sunrise ; and such changes 

 happened several times along the route. 



To the eastward, beyond the Cascade Range and Sierra Neva- 

 da, the country is more elevated and colder ; and the climate be- 

 comes gradually more and more dry towards the summit of the 

 Rocky Mountains, being excessive in its drought to the south 

 about the region of the Colorado. There are at long intervals 

 green spots that admit of cultivation by irrigation. 



Over the Great Basin, Fremont found a cool climate, though 

 less so, for the season, notwithstanding its height, than in East- 

 ern America. Crossing it in November, 1845, (5th to 25th), be- 

 tween latitudes 41° and 38°, the mean temperature at sunrise 

 was 29°, and at sunset 40°. Excepting a snow storm between 

 the 4th and 7th, the weather was uninterruptedly clear until the 

 close of the year, without rain or snow. He observes also that 

 J "the winter of 1843, 1814, within the basin, was remarkable 



for the same open, pleasant weather, rarely interrupted by ram 



or snow."* 



Emory, in the month of November along the Gila, had general- 







ly clear weather, with rain but twice. The temperature on Nov. 

 23 and 24, near the mouth of the Gila, varied from 40° to 69° 

 F. ; (40° at 6 a. m.) On the morning of the 25th, it was at 27° 

 F. ; morning of the 26th at 5 a. m. on the Jornada, 21° F., and 

 60° F. at 5 p. m. A desert was passed between the Rio Colo- 

 rado and the mountains east of San Diego. 



It has not been our purpose to present a full account of the 

 meteorology of the region. We have cited a few facts only in 

 illustration of the general views here presented. 



The great difference between the mean temperature of the east 

 and west coasts of America is a fact well known. Vancouver in 

 latitude 45° 40', has nearly the temperature of Baltimore in lati- 

 tude 39° 22', and generally, the difference corresponds to six or 



Geographical Memoir upon Upper California, p. 1 3 



