264 J. EF. Marr—Origin of Archean Rocks. 
If this theory be accepted, it raises very serious difficulty in the 
way of accounting for the Archean rocks, upon the supposition that 
they were deposited in the sea. Mr. W. K. Gilbert (Nature, vol. 
xxvii. p. 262) has insisted upon the fact that wherever the Archean 
rocks are found, succeeded by newer formations, there is an uncon- 
formity between the two. This means that in early Cambrian times, 
the localities where Archean rocks are found succeeded by Cambrian 
rocks (and they are many, and widely distributed) were occupied by 
land. On the other hand, in Pre-Cambrian times, these areas were 
occupied by ocean, if the Archean rocks are oceanic deposits. But 
since the Archean rocks are so widely spread over our present con- 
tinental areas, where was the land, the denudation of which supplied 
the material for these rocks? It must almost necessarily have 
occupied the sites of our present oceans, unless we suppose that 
these land surfaces lay in every case in those areas which are now 
covered by newer rocks. This goes against the theory of the per- 
manence of the sites of oceans and continents, for in Archean times 
the present continental areas were occupied by great oceans (always 
assuming the oceanic formation of these rocks), and the present 
oceanic areas by land, whilst at the end of Archean times, our 
present continental areas were converted into land. 
Objection may be raised that the Archean rocks were not being 
formed simultaneously in different areas. If this be so, the occur- 
rence in so many areas of a series of highly altered gneissose and 
other rocks, succeeded by a less highly altered series of green more 
or less schistose rocks, is a singular coincidence. Again, it may be 
objected that newer rocks of different ages were deposited uncon- 
formably upon the Archean rocks, for instance, in Westrogothia, the 
Fucoid sandstones rest unconformably upon them; in parts of 
Bohemia, the sandstones below stage C, and in other parts the band 
D. d la. ; whilst in Britain, we find Harlech beds at St. Davids, 
Lingula flags at Malvern, Arenig rocks at Carnarvon, ete. But this, 
as shown by Dr. Hicks (Quart. Journ. Geol. Soc. vol. xxxi. p. 552), 
indicates the submergence of successive portions of a sloping 
Archean land, rather than successive upheavals of different parts of 
an Archean ocean-floor. If the break were not produced in all areas 
simultaneously, it is exceedingly difficult to account for the entire 
absence of ordinary unmetamorphosed marine sediments of Archzean 
age. 
8. The theory of the growth of continents by successive additions 
along their borders, advocated by Dr. Dana in North America, seems 
with slight modifications to be applicable to the European continent 
also. The Cambrian and Silurian rocks stretch far eastward into 
Russia, and are found north as far as Jemtland in Sweden, and above 
Bergen in Norway, and as far south as Spain and Sardinia, usually 
as wide-spread marine deposits. In Devonian and Carboniferous 
times, various ridges of land existed in this ocean, and in Mesozoic 
times the site of the European continent was occupied by wide 
Mediterranean Seas, as shown by Mr. Wallace (Island Life, p.87). 
In Tertiary times, the continent was so far compacted, that it was 
