XXII REPORT UNITED STATES GEOLOGICAL SURVEY. 



2. The Pacific slope, subdivisible into (a) a very humid, cool, forest-clad coast range ; 

 (/3) the great, hot, drier Californiau valley, formed by the San Juan River flowing to 

 the north, and the Sacramento River flowing to the south, both into the Bay of San 

 Francisco ; and (y) the Sierra Nevada flora, temperate, subalpine, and alpine. 



3. The Rocky Mountain region (in its widest sense extending from the Mississippi 

 beyond its forest region to the Sierra Nevada), subdivisible into (a) a prairie flora, (/?) 

 a desert or saline flora, (y) a Rocky Mountain proper flora, temperate, subalpine, and 

 alpine. 



As above stated, the difference between the floras of the first and second of these re- 

 gions is specifically, and to a great extent generically, absolute ; not a pine or oak, 

 maple, elm, plane, or birch of Eastern America extends to Western, and genera of 

 thirty to fifty species are confined to each. The Rocky Mountain region again, though 

 abundantly distinct from both, has a few elements of the eastern region and still more 

 of the western. 



' Many interesting facts connected with the origin and distribution of American plants, 

 and the introduction of various types into the three regions, presented themselves to 

 our observation or our minds during our wanderings. Many of these are suggestive of 

 comparative study with the admirable results of Heer's and Lesquereux's investiga- 

 tions into the Pliocene and Miocene plants of the north temperate and frigid zones, 

 and which had already engaged Dr. Gray's attention, as may be found in his various 

 publications. No less interesting are the traces of the influence of a glacial and a 

 warmer period in directing the course of migration of Arctic forms southward, and 

 Mexican forms northward in the continent, and of the effects of the great body of 

 water that occupied the whole saline region during (as it would appear) a glacial 

 period. 



Lastly, curious information was obtained respecting the ages of not only the big 

 trees of California, but of equally aged pines and junipers, which are proofs of that 

 duration of existing conditions of climate for which evidence has hitherto been sought 

 rather among fossil than among living organisms. 



ARCHAEOLOGY. 



Up to tlie year 1874 rumor had been telling many marvelous stories 

 of strange and interesting habitations of a forgotten people, who once 

 occupied the country about the headwaters of the Eio San Juan, but 

 these narrations were so interwoven with romance that but few people 

 placed much reliance upon them. To those well versed in archaeology, 

 ruins of an extensive and interesting character were known to exist 

 throughout New Mexico and Arizona, and the various reports of Abert, 

 Johnson, Sitgreaves, Simpson, Whipple, Newberry, and others form our 

 most interesting chapter in ancient American history; but their re- 

 searches, aside from the meager accounts published by Newberry, throw 

 no light on the marvelous cliff dwellings and towns north of the San 

 Juan. In 1874 the photographic division of the United States Geolog- 

 ical Survey was instructed, in connection with its regular work, to visit 

 and report upon these ruins, and in pursuance of this object made a 

 hasty tour of the region about the Mesa Verde and the Sierra el Late, in 

 Southwestern Colorado, theresults of which trip, as expressed by Ban- 

 croft, in the Native Races of the Pacific Coast, "although made known 

 to the world only through a three or four days' exploration by a party 

 of three men, are of the greatest importance." A report was made and 

 published, with fourteen illustrations, in the Bulletin of the United 



