184 
IDDI'NGS. 
are poor in alkalies. In the sub-alkali group are included 
natural groups, the great majority of whose members are 
relatively poor in alkalies, while a few may be comparatively 
rich in alkalies. This grouping is selected merely for present 
purposes, and is not suggested as a possible basis of classifi¬ 
cation, since it is too indefinite. 
Sub-alkali groups of rocks extend over a large part of the 
Great Basin of western America and the Pacific coast into 
Mexico and Central America, and it is probable that the 
rocks of the Andes, in South America, belong to the same 
group; but it is possible that this belt is not an uninter¬ 
rupted one, and may be broken into smaller areas of some¬ 
what different characters, for it is known that leucite rocks 
occur in Lower California. 
Alkali groups occur along the eastern part of the Rocky 
mountains and are known in Montana, Wyoming, South 
Dakota, Colorado, and a variety of them is developed in 
Arizona. Rocks of the alkali group, notably eleolite-syenites 
and associated varieties, occur in the central and eastern 
United States and Canada, having been found in Arkansas, 
New Jersey, Massachusetts, and Maine, and in the vicinity 
of Montreal. They are specially characteristic of Brazil and 
the islands off the east coast of South America, and nephe- 
line and leucite basalts have been found along the eastern 
part of the Andes, in Argentine Republic, and Paraguay. 
In Europe the region of alkali rocks is better known than 
that of the sub-alkali group. The former extends from the 
Scandinavian peninsula, through Germany, Bohemia, Aus¬ 
tria, and France to Portugal, and continues across the north¬ 
western part of Africa to the islands along its western coast. 
Sub-alkali groups are characteristic of Great Britain and 
Hungary, and probably extend for a considerable distance 
eastward and southeastward, including the Grecian archi¬ 
pelago and the Caucasus, extending into Persia. 
Alkali rocks occur in Kerguelen island and in southeast¬ 
ern Africa and the islands to the eastward. They also occur 
in Java. 
