508 



A TREATISE ON METAMORPHISM. 



Supposing the amount of aluminum to be constant (except in Table 

 III, analysis 2, fresh diabase from Venezuela, in which iron is supposed to 

 be constant), the original composition and the losses of the various elements 

 for the following' rocks are as follows: 



Table II. — Analyses of fresh and altered gneiss and syenite. 



