26 SCIENCE PROGRESS. 



Farther south, however, in the Cape Verde Islands, 

 Canaries, and Azores, we find rocks of the alkaH-group, 

 and again on the Atlantic coast of Africa. Rocks of the 

 same group are recorded in various districts on the east 

 coast of Africa, including Madagascar, and as far north at 

 least as Massai Land and Kilimanjaro. On the other hand, 

 almost the whole area of the Pacific Ocean and its borders 

 seems to be characterised by sub-alkali rocks, though a few 

 nepheline-basalts have been noted from some of the islands. 

 Concerning the polar oceans our information is very in- 

 complete. The elseolite-syenites and allied rocks of Green- 

 land show that types rich in alkalies have at one time been 

 well represented within the Arctic circle, and the little that 

 is known of the petrology of the far south suggests the 

 probability that the Antarctic is also an area of alkali- 

 rocks. Leucite-bearing rocks are found even in New 

 South Wales, though the age of these is not known, and 

 they recur in Java and Celebes, coming there into close 

 proximity with andesitic and other types belonging to the 

 great Pacific region. The leucite-bearing rocks of 

 Trebizonde appear at present to occupy an anomalous 

 position. 



If the distribution of the two groups of rocks thus briefly 

 outlined be laid down in greater detail on a map and 

 distinguished by different colours, a remarkable fact be- 

 comes apparent. This is the very general correspondence 

 of the areas of the alkali and sub-alkali groups respec- 

 tively with the areas of the Atlantic and Pacific types 

 of coast-line as defined by Suess. The one type is found 

 around the Atlantic and part of the Indian Ocean and in 

 the Polar basins, the other, generally speaking, around the 

 Pacific. Whether we may have to recognise an Atlantic 

 and a Pacific facies of eruptive rocks, corresponding with 

 distinct phases in crust-movements of a large order, is a 

 question which it would be premature to answer at present; 

 but it is at least clear that the distribution, not only of 

 igneous rocks in general, but to some extent of different 

 petrographical groups of rocks is in some way bound up 

 with disturbances of the earth's crust or with the forces that 



