124 GEOLOGY OF PATAGONIA. [CHAP. vin. 



feet. If this great bed of pebbles, without including the mud neces- 

 sarily derived from their attrition, was piled into a mound, it would 

 form a great mountain chain ! When we consider that all these pebbles, 

 countless as the grains of sand >n the desert, have been derived from 

 the slow falling of masses of rock on the old coast-lines and banks of 

 rivers ; and that these fragments have been dashed into smaller pieces, 

 and that each of them has since been slowly rolled, rounded, and fai 

 transported, the mind is stupefied in thinking over the long, absolutely 

 necessary, lapse of years. Yet all this gravel has been transported, 

 and probably rounded, subsequently 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 

 1,200 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 3,000 feet at the foot of the Cordillera. I have said 

 that within the period of existing 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 1,500 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 1,000 feet in thick- 

 ness : 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 on the go- 

 feet plain, I found half the skeleton of the Macrauchenia Patachonica, 

 a remarkable quadruped, full as large as a camel. It belongs to the 

 same division of the Pachydermata with the rhinoceros, tapir, and 



* I have lately heard that Captain Sulivan, 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 

 discpvery, 



