1253 
Rio de Janeiro together with picrite porphyrites, alnoites and lim- 
burgites, besides similar rocks in dykes and pipes in the Western 
part of the State Minas Geraes '). 
Just as the Kimberlite rocks near the West-Coast of South-Africa, 
the known Brazilian rocks also belong nearly all to the basaltic 
varieties, which are poor in mica. ; 
Horizontal movement of the Atlantic Coasts. 
The resemblance between some groups of sedimentary rocks on 
either side of the Atlantic Ocean is also striking. We merely men- 
tion the South-African Karroo System and the Brazilian Santa 
Catharina System. The Orleans conglomerate in Sta. Catharina and 
Rio Grande de Sul agrees with the Dwyka conglomerate of South- 
Africa and in either continent the higher divisions are built up of 
the above-named thick series of voleanic rocks, such as those of the 
Drakensberg in Cape Colony and those of the Serra Geral in Rio 
Grande de Sul. 
When we reconstruct the volcanoes of alkali rocks which existed 
in earlier periods along the present coasts, and imagine the two 
continents to be brought close together, we obtain a configuration 
similar to the aspect of the East-African Lake region, where at the 
present day the voleanoe Kenia and Kilima Ndsjaro built up of 
alkali-rich rocks, arise. This picture illustrates WEGENER’s*) inter- 
pretation of the origin of the Atlantic Ocean *). More should be 
known, than has been recorded in the foregoing, about the resem- 
') KE. Rimann. Uber Kimberlite und Alnoite in Brasilien. Tscherm. Min. u. Petr. 
Mitt. 1915. Id. A Kimberlita no Brazil. Annaes da Escola de Minas de Ouro 
Preto. N°! TS: TOT.“ blz. 21 e.V. 
2) A. Wecener. Die Entstehung der Kontinente und Ozeane, Die Wissenschaft, 
Bd. 66, 1920. 
3) Still other fissures of the African continent may be reconstructed of similar 
character to, but of higher geological age than, those of the present East African 
fractures. We refer to the system of dykes of alkalierocks with a uniform north- 
western to northern trend, occurring on either side of the old volcanic centre of 
the Pilands Berg in the Transvaal and can be traced over a distance of more 
than 100 K.M., cutting through all older formations. In the part of the earth’s 
crust, which has disappeared here through erosion the fault-system may have 
‘ exhibited here an aspect similar to that of parts of the present East-African 
fracture-system ; it seems however that the horizontal movements on either side 
of these faults soon ceased and that they did not produce any considerable gaps. 
Then the fissures will disappear at greater depths and many similar faults may 
have existed in an earlier stage of erosion on the African Continent as intruded 
or gaping, fissures, of which no trace is visible now. (Cf. fig. 2 and p. 765 in 
H. A. Brouwer, Geology of the Alkali rocks ete. 1. c.) 
