468 THE AMERICAN NATURALIST. 
The author points out the practical identity in the composition of 
the wyomingite and orendite, and concludes from this identity “ that 
chemical composition of a magma does not alone determine whether 
leucite or sanidine shall be formed, but that this is controlled by 
conditions of consolidation.” 
A reclassification of leucite rocks is proposed, based on the quan- 
titative importance of the leucite in them. The term leucitite is 
reserved for rocks in which leucite is the predominant component. 
Wyomingite and its granular equivalent are rocks in which leucite is 
of approximately equal importance with the ferro-magnesian-lime 
silicates. _Orendite contains sanidine and leucite in about equal 
quantities. Both of these rocks are rich in silica. In madupite the 
heavy silicates predominate, leucite being in subordinate quantity. 
Its magma is low in silica. 
Inclusions in the wyomingite and the orendite have been subjected 
to considerable contact action, the feldspars in the inclusions having 
suffered more than the bisilicates. 
