532 CEXOZOIC TIME. 



Western and Southern North America. — In the Rocky Mountains, 

 the Sierra Nevada, and other western ranges, there are scratches, 

 polished rocks, and roches moutonnees of vast extent, as well as the 

 local Drift alluded to on page 528 ; and, like the Drift, they have, in 

 general, the courses of the valleys or slopes. On Vancouver's Island, 

 near Victoria, however, the scratches have a south-southwest course 

 (magnetic), and others a south-southeast; and these may be connected 

 with a true northern Drift. 



Scratches and polishing of rocks, of limited extent, have been observed by R. P. 

 Stevens, either side of the Alleghanies, in West Virginia, accompanying the Drift de- 

 scribed as occurring there, on page 528. 



The scratched and polished rocks of the Sierra Nevada are of great extent and per- 

 fection, about Mount Lyell and several other higher summits of the Sierra Nevada, as 

 described by Whitney, King, and Le Conte. They are very remarkable also about the 

 Crest range of the Rocky Mountains, in Colorado, as observed by Hayden & Gardner. 

 A portion of one of the valleys leading away from the Mountain of the Holy Cross 

 (covered with " sheep- backs ") is represented in Fig. 1106, on page 685, from a sketch 

 from Hayden 's Report. 



3. Forced Migration of Plants. — On the summits of the White 

 Mountains, the Adirondacks, and some peaks of the Green Mountains, 

 and other places, less elevated, there are species of subalpine plants, 

 which are believed to have migrated southward in Glacial times. 



Thirty-seven kinds, according to Dr. Asa Gray, 1 occur on the White Mountains 

 alone, and part of them on the Adirondacks and Green Mountains. Besides these, 

 Sedum Rhodiola D. C, a subalpine species, occurs on cliffs of the Delaware, below Eas- 

 ton, Pa.; Saxifraga oppositifolia Linn., on Mount Willoughby, in Vermont; Arenaria 

 Grbnlandiea Sprengel, a Greenland species, is found on the top of the White Mountains, 

 the Catskills, Shawangunk Mountain, and, in the form of A. glabra Michx., on the Al- 

 leghanies of Carolina; Scirpus cais/ntosus Linn., alpine and subalpine, has a patch re- 

 maining on Roan Mountain, North Carolina; Nephroma Arcticum Fries, and other 

 northern Lichens, with Lycopodium selago Linn., still live on the highest Alleghanies. 



2. Drift in Foreign Countries. 



The Drift material presents the same characteristics on the other 

 continents as in North America. It is confined to the northern half 

 of Europe ; that is, Britain, Denmark, Scandinavia, Russia, Poland, 

 and northern Germany, down, in some portions, to the parallel of 

 51°, — a line which has nearly the same mean temperature now as the 

 southern limit, 39°, in the eastern United States. In South America, 

 it is met with, from Tierra del Fuego, as far toward the equator as 

 37° S., and especially, as Agassiz has shown, in the great valley be- 

 tween the main chain of the Andes and the Coast Mountains, where 

 it was observed by him, to the latitude of Concepcion. It occurs like- 

 wise on the east side of the Andes ; also over parts of New Zealand. 



l American Journal of Science, II. xxiii., 62, 1857. 



