194 GEOLOGY OF OLD HAMPSHIKE COUNTY, MASS. 



absorption and jjleoclaroism; extinction, 16° 30'. These lie in a mosaic of 

 untwiuned feldspar grains. Menaccanite and leueoxene are abundant, and 

 in slides from the south end of the bed in Williamsburg (south of P. M. 

 Gillett's) each grain of menaccanite is surrounded by a single crystal of 

 leueoxene, and these often have the regular wedge-shape of titamte. 



East of C. Bardwell's the rock abounds with white spots which prove 

 to be a quartz-feldspar mosaic, greatly crowded with many impurities, but 

 with clear borders. The hornblende is in sheafs and bundles of fine fibers, 

 which partly coalesce into stout crystals, so that the transverse parting runs 

 across the bundle and the center polarizes as a single individual. The cen- 

 tral portion of these large crystals is full of coaly particles. Pleochroism 

 and absorption are weak. Biotite and rarely a congeries of grains of 

 leueoxene occur. This occurrence agrees clearly with the hornblende- 

 schist derived from the calcite beds described above, and I assign this origili 

 to all the hornblendic beds in the Conway schist, particularly as limestone 

 is abundant and all other traces of basic eruptives are wanting. 



All these rocks share with the accompanying micaceous schist the pecul- 

 iarity that the centers of the larger phenocrysts are full of coaly matter or 

 fine quartz grains, indicating that both have together passed through two 

 stages in the metamorphic process. 



This peculiarity is wanting in the similar amphibolites of the Bernards- 

 ton series (see p. 291), with which I would compare these rocks. The latter 

 series, though of later age geologically, is more metamorphosed and differs 

 in the more abundant development of the clear mosaic of untwinned 

 plagioclase, but in no other way. They have the same field relations, 

 the amphibolite being always interbedded in the schists. They have the 

 same abundant actinolitic hornblende, biotite, ilmenite with leueoxene, 

 rutile with dark border, and basic plagioclase, and range from massive to 

 slaty varieties. 



At Mrs. M. Taylor's, in Whately, the rock is fine-grained and thin-fissile. 

 Its long, thin hornblende needles have low absorption and pleochroism, and 

 lie in a feldspar mosaic. A great number of titanite grains inclose one or 

 more grains of black ore. For section, see PI. VI, fig. 1, p. 306. 



(ff) The Whitmores Ferry amphibolite. At Whitmores Feny, in North 

 Sunderland, in the midst of the Triassic shales, arises an outcrop of a dark 



