434 Capt. F. W. Hutton on the Origin of the 
put the South-Pacific continent later than the Cretaceous 
period. On the other hand, though fossil plants belonging to 
the Jurassic period are known from many parts of the world, 
not a single Dicotyledon has as yet been found among them, the 
oldest known form being a poplar from the Lower Cretaceous 
beds: of Greenland. In the Upper Cretaceous epoch dico- 
tyledonous plants were abundant in Europe, North America, 
and in tropical Africa, and each of the three classes Mono- 
chlamydez, Polypetale, and Gamopetale were represented. 
The South-Pacific continent must therefore have existed after 
the Jurassic, and must have been submerged before the 
Eocene period. 
Let us now see what light the geology of the surrounding 
countries throws on the subject. ‘To commence with Chill: 
from Mr. Darwin’s ‘ Observations on the Geology of South 
America’ we learn that the fundamental rock-system of Chili 
and Western Tierra del Fuego consists of an irregular plateau 
of mica-schist and gneiss. On this floor immense masses of 
volcanic rocks, chiefly andesites and diorites, have been poured 
out from submarine volcanoes, forming the ranges of moun- 
tains called the Andes. ‘These mountains are highest in the 
north, and get lower and lower southwards ; but portions of 
volcanic rocks are found all through to Tierra del Fuego. 
High up among the volcanic rocks of the Andes in Chili a 
sedimentary gypseous system occurs, containing fossils of the 
Lower Cretaceous or perhaps Upper Jurassic period. Fossils 
of the same age are also found in a clay-slate system forming 
the eastern side of Tierra del Fuego and stretching far up the 
eastern flanks of the Andes. These Lower Cretaceous rocks 
go toa height of 14,000 or 15,000 feet above the sea. On 
the Atlantic side enormous plains of gravel and silt slope 
from the sea to an elevation of 8000 feet or more at the 
base of the mountains. On the Pacific side horizontal strata 
of probably Eocene age lie on the older rocks, and_ these 
are covered in places by gravel-beds, which go to a height of 
1300 feet. 
From these facts Mr. Darwin infers that during the Juras- 
sic period this part of South America was a deep sea, on the 
bed of which volcanic eruptions took place. In the Lower 
Cretaceous it was shallow sea, with land in the neighbourhood, 
but the bottom was sinking, and it was further depressed for 
7000 or 8000 feet, although the volcanic ejections continued 
to maintain land above the surface of the ocean. In the 
Upper Cretaceous period upheaval commenced, and, although 
interrupted by many oscillations, this upheaval has been 
going on ever since, until the elevation has been as much as 
