PLATE III. 



Fig. 1. — Leyden argillite changed to chiastolite-schist in contact on tonalite. Only the black cross of 

 the ehiastolite remains. The crystals have been changed into a mass of muscovite scales inclosing 

 many staurotite crystals. Belmont, Hatfield. x7. Natural light. (Seep. 209.) 



Fig. 2. — Sections of twins of cordierite from cordierite-granite, Brimfield. X20. Drawn with crossed 

 nicols. (Sec p. 321.) 



Fig 3. — Diorite from north end of Packards Mountain, Prescott. x25. Natural light. (Seep. 342.) 



Fig. 4. — Contact of diabase-amygdaloid aud clayey limestone, from the upper surface of the Holyoke 

 sheet. The curving of the layers of the fine mud as it flowed into the open steam holes can be seen 

 on the left. The large cavity was clogged by a trap fragment and afterwards filled by infiltrated 

 calcite. Rounded drops of the mud and rounded holes filled by infiltration can be seen in the 

 trap C, Dibbles, South Holyoke. X28. (See p. 456.) 

 208 



