474 H. B. PATTOX — THOMSONITE, MESOLITE, AND CHABAZITE 



in successive deposits in the same cavity. The thomsonite is chiefly 

 remarkable for the great variety of types in which it occurs, each type 

 representing a distinct generation. A microscopical investigation indi- 

 cates that the brachypinacoid is the dominant form, instead of the 

 macropinacoid, as formerly 'supposed. 



The mesolite is distinguished both by great variety of type and by 

 exquisite beauty and delicac} 7- . Chabazite occurs in crystals that show 

 twinning parallel to the basal plane and an unusual development of 

 forms. 



The zeolites, together with calcite and aragonite, as they occur here, 

 indicate no less than fifteen distinct stages or periods of mineral depo- 

 sition. 



