X CONTENTS. 



Page. 



C'HAPTEU X. — Thi' ampbibolites described in the preceding chapters 300 



Analyses aud sections 300 



Porphyritic character of the ampbibolites 304 



Chapter XI. — The eruptive rocks 307 



Introduction 307 



Historical notes on the mica-granites 312 



Biotite-musoovite-granite 314 



Areas west of the Connecticut 314 



Distribution 314 



Petrographical description 315 



Chemical analysis 315 



The Athol area 316 



Secretions and inclusious 317 



The Hardwick gneissoid granite and granitite 317 



Biotite-granite, or granitite 318 



Contact metamorphism of the granitite and schists 318 



The Middletield porphyritic granitite 318 



The Coy's Hill porphyritic granitite 31!) 



Description and distribution 31"J 



C'ordierite-granitite 321 



Muscovite-granite, or pegmatite 322 



Probable extreme modification of the pegmatite by crushing 323 



Albitic granite and pegmatite dikes containing rare minerals 323 



Distribution aud description 324 



The great tourmaline-spodumene dike 324 



Dikes in Goshen 326 



Dikes in Chester, Blandford, and Huntington 327 



Dikes east of the Connecticut 327 



Garnet in pegmatite with complex paramorphic border of zoisite-hematite, epidote- 



flbrollte, and muscovite 328 



The crushing of minerals in the albitic granite 329 



Hydrothermal changes in the albitic granite veins 329 



Ordinary meteoric alteration 330 



Aplite 331 



Quartz-gabbro and quartz-diorite, or tonalite 331 



Historical 331 



Basic secretions: Hitchcock's suggestion of the theory of "schlierengange" 331 



Distribution 335 



Analyses of tonalite 336 



Petrographical description 336 



The crushing and alteration of the tonalite along the Pelham fault 339 



Petrographical description of the altered tonalite 341 



Diorite 342 



Garnet-biotite-norite 345 



Cortlaudite 346 



Age of' the granites 348 



Rtfisum*' as to the genetic relations of the granites 348 



Contact effects of the eruptive rocks 349 



