ANNIVERSARY ADDRESS OF THE PRESIDENT. IxXlil 



Desire, there are seven such terraces^ separated by plams of various 

 breadths, sloping, though seldom sensibly so to the eye, from the sum- 

 mit of one escarpment to the foot of the next above. The three 

 lower plains are respectively 100, 250, and 350 feet above the sea- 

 level, and the highest of the other four was estimated to be 1200 feet 

 in height. These elevated terraces and plains extend horizontally to 

 vast distances : one ranging from 245 to 255 feet in height appears 

 to extend with much uniformity a distance of 170 miles ; another, 

 estimated at a height of from 330 to 355 feet, extends over a space 

 of 500 miles in a north and south line ; one in the middle of the great 

 Bay of St. George, estimated at 1200 feet in height, was seen ranging 

 at apparently the same height for 150 miles northward, and some 

 approximate measurements indicate an extension of the first-named 

 terrace to 780 miles. These upraised plains are all strewed with shells 

 of littoral species, still existing as the commonest kinds in the ad- 

 joining sea; Mr. Darwin saw them at a height of 410 feet, and he 

 does not know, he says, that that is the maximum height of these 

 remains. '^ All of them have an ancient appearance ; but some, 

 especially the muscles, although lying fully exposed to the weather, 

 retain to a considerable extent their colours. Most of the shells are 

 broken, and the valves are not united ; but the fragments are not 

 rounded*/' 



There thus appears to have been a most remarkable equability in 

 the elevation of thfcse several terraces over a vast area, and the periods 

 of the denudation of the sea-cliffs, which form the escarpments of 

 the terraces, were synchronous along wide extents of coast. It is 

 probable, therefore, that the elevation was by slow and insensible 

 degrees, of which there are some further proofs. Thus on some of 

 the plains there are sand-dunes, at different levels, abounding with 

 shells ; and in none of the coast and river sections is there any fault, 

 or abrupt dislocation, or any curvature in the strata. From the 

 quantity of matter that must have been removed by the action of the 

 waves on the shore to form each successive escarpment, it is no less 

 evident that there must have been long periods of rest in the elevatory 

 movement — that it was not constant, but intermittent, as we know to 

 be the case in other countries, and as we find to have been the case, 

 even within the historical period, on the western coast of this conti- 

 nent. 



The elevations of the coast of Patagonia began after the adjoining 

 sea was inhabited by the most common and abundant of the existing 

 species of littoral shells, but before the introduction of living mam- 

 mifers. The remains of extinct mammifers have been fomid in the 

 lowest plain, in hollows worn in the gravel beds, which are filled 

 by a reddish sandy earth, the same as that which caps the general 

 surface of the gravel. It would be interesting to find out whether 

 similar remains exist in the higher plains ; for if they do not, it 

 would mark, approximatively, that the introduction of the mammifers 

 took place long after the creation of the living species of moUusca. 



There are proofs no less evident of elevations of the land on the 

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