176 GEOLOGICAL MOVEMENTS, [chap. viii. 



the long, absolutely necessary, lapse of years. Yet all this 

 gravel has been transported, and probably rounded, sub- 

 sequently to the deposition of the white beds, and long 

 subsequently to the underlying beds with the tertiary shells. 



Everything in this southern continent has been effected 

 on a grand scale : the land, from the Rio Plata to Tierra 

 del Fuego, a distance of 1200 miles, has been raised in mass 

 (and in Patagonia to a height of between 300 and 400 feet), 

 within the period of the now existing sea-shells. The old 

 and weathered shells left on the surface of the upraised plain 

 still partially retain their colours. The uprising movement 

 has been interrupted by at least eight long periods of rest, 

 during which the sea ate deeply back into the land, forming 

 at successive levels the long lines of cliffs or escarpments, 

 which separate the different plains as they rise like steps 

 one behind the other. The elevatory movement, and the 

 eating-back power of the sea during the periods of rest, 

 have been equable over long lines of coast ; for I was 

 astonished to find that the step-like plains stand at nearly 

 corresponding heights at far distant points. The lowest 

 plain is 90 feet high ; and the highest, which I ascended 

 near the coast, is 950 feet ; and of this, only relics are left in 

 the form of flat gravel-capped hills. The upper plain of 

 Santa Cruz slopes up to a height of 3000 feet at the foot of 

 the Cordillera. I have said that within the period of exist- 

 ing sea-shells Patagonia has been upraised 300 to 400 feet : 

 I may add, that within the period when icebergs transported 

 boulders over the upper plain of Santa Cruz, the elevation 

 has been at least 1500 feet. Nor has Patagonia been 

 affected only by upward movements : the extinct tertiary 

 shells from Port St. Julian and Santa Cruz cannot have 

 lived, according to Professor E. Forbes, in a greater depth 

 of water than from 40 to 250 feet ; but they are now covered 

 with sea-deposited strata from 800 to 1000 feet in thickness : 

 hence the bed of the sea, on which these shells once lived, 

 must have sunk downwards several hundred feet, to allow 

 of the accumulation of the superincumbent strata. What a 

 history of geological changes does the simply-constructed 

 coast of Patagonia reveal ! 



At Port St. Julian, * in some red mud capping the gravel 



* I have lately heard that Captain Sulivaa, R.N., has found numerous 

 fossil bones, embedded in regular strata, on the banks of the R. Gallegos, in 

 lat. 52* 4'. Some of the bones are large ; others are small, and appear to 

 have belonged to an armadillo. This is a most interesting and important 

 discovery. 



