on their edges to (lib. rite, a little biotite. magnetite and apatite. The 

 compaction of one of these is given as: 



SiO, ALA Fe,0 3 FeO CaO MgO K<> Na .< > H<» 



The phonolites are fine-grained rocks, made up of porphyritic crys- 

 tals of acmite and red augite, sometimes zonally iutergrown, and horn- 

 blende, in a ground mass consisting of microlites of hornblende, 

 augite, biotite, orthoclase, plagioclase, muscovite and magnetite, and 

 little grains of a colorless mineral, probably orthoclase, in an isotropic 

 base. Nepheline could not be detected microscopically, but is supposed 

 to be present as the result of chemical tests. One specimen contains 

 regularly outlined icositetrahedra composed of a nucleus of calcite 

 and sahlite, and an external zone of biotite, that are regarded as altered 

 garnets. Since this rock occurs between a well characterized phonolite 

 ami limestone it is thought to be a eontaet facies of the former. 



The trachytes, andesites, basalts, etc. of the Upper Eifel have been 

 subjected to a very careful in vestigation by Vogelsang/' The phono- 

 lite and the leucite and nepheline lni>anit< - have no peculiar charac- 

 teristics which need be referred to here. The basalts include plagio- 

 clase, leucite and nepheline varieties, the former two of which have 

 effected alteration in sandstones and graywackes. with which they are 

 in contact. The trachytes are very much like the Drachenfels rock, 



