LIST OF FIGURES. 243 



Figs. 4 and 5. Diagrams of the bases of two of the immense beryls from Graf- 

 ton, giving the dimensions in inches (Hubbard)— page 67. 



Fig. 6. Crystal of cassiterite from Jackson (Teschemacher)— page 44. 



Fig. 7. A cleavage face on the green octahedral fluor spar from the Notch. 

 a and b etch figures, c and d cavities partially filled with water- 

 page 35. X 30 



Figs. 8 and 8^. Diagrams illustrating the mode and effect of the polysynthetic 

 twinning of triclinic feldspars — page 86. 



Fig. 9. Muscovite enclosing a crystal of biotite, from Alstead (Rose)— page 84. 



Fig. ID. Diagram indicating the relationship of the natural cleavage lines, which 

 often divide large plates of mica, to the crystalline form, and the 

 cause of this cleavage — page 84. 



Plate IV. 



Fig. I. Crystals of rutile in a section of actinolite schist from Pittsburg. Fine 

 black acicular crystals in the quartz ; larger, yellow, in part twin 

 crystals in the actinolite — page 46. x 200 



Fig. 2. Section of hypersthene in gabbro from Waterville, showing its charac- 

 teristic interpositions and the method of their arrangement— page 55. x 50 



Fig. 3. Augite crystals in a section of porphyritic diabase from Campton falls- 

 page 56. X 30 



Fig. 4. Basal section of a large crystal of beryl from Grafton, showing its en- 

 closures — page 69. X 200 



Fig. 5. A section through an apparently pure crystal of garnet, in hornblende 



schist from Hanover — page 74. x 20 



Fig. 6. The diatoms which compose the beds of infusorial earth. Drawn by 

 Ehrenberg from a New Hampshire specimen — page 52. Highly 

 magnified. 



Plate V. 



Crystals of zircon in a section of the Fitzwilliam granite— page 75. x 200 



Crystals of muscovite in a section of the Roxbury granite — pages 86 



and 195. X 50 



Section through a crystal of anorthite in diabase from East Hanover, 

 showing the progress of alteration — page 91. x 30 



Section of labradorite from Stark, showing two systems of polysyn- 

 thetic twinning — page 93. x 50 



Section of labradorite in gabbro from Waterville, showing crystallites 

 and their method of arrangement — page 94. x 50 



Triclinic feldspar interlaminated with orthoclase, as seen in a section 

 of the Concord granite — pages loi and 194. x 30 



