580 STRATIGRAPHICAL GEOLOGY. 



and gradually increases to nearly four in Temple and Wilton. The dip 

 is invariably north-westerly, and usually at a small angle. It forms a 

 sort of plateau through Mont Vernon. Roby hill, in the north-west part 

 of the town, is composed of mica schist. It crops out with a low, north- 

 westerly dip at A. J. Twiss's and B. Jones's, near a mill ; a mile north- 

 east from the village ; at the church, with granite ; near G. A. Wallace's, 

 on the Francestown road; near J. Hartshorn's, dip 15° N. W. ; near A. 

 Upton's, and elsewhere. At Purgatory falls, on the line of Mont Vernon 

 and Lyndeborough, the schists, with coarse granite beds, dip 50° N. 30° 

 W. In the north-east corner of Wilton the dip is small to the north- 

 west. This range is made to terminate in the north part of New Ipswich, 

 but it may possibly continue into Massachusetts, On the north-east it 

 points towards the Allenstown deposit, and may occupy the same depres- 

 sion with that or some portion of it. 



Temple Mountain Range, The map shows a line of elevations from 

 Lyndeborough to New Ipswich, whose similar topographical features 

 suggest identity of geological character. The Lyndeborough mountains 

 rise abruptly from the comparatively flat ground of New Boston and 

 Francestown ; and the rocks change as quickly as the elevation. Gneiss 

 is exchanged for mica schist. We observed the following facts in cross- 

 ing from Francestown to the centre post-office : Irregularly curved mica 

 schists, like those holding andalusite, with westerly dip, on the Piscata- 

 quog river near the south line of Francestown ; at L. Spaulding's, a 

 mile farther, the mica schists dip north-west at a small angle ; on the 

 summit of the ridge the dip is 50° N. 20° W.; and the same rock extends 

 nearly to the centre village. Loose blocks of the schist hold excellent 

 specimens of the long, fibrous mineral andalusite or fibrolite, showing 

 that it characterizes the deposit, though not actually found in place. 

 Between the Pinnacle and Pack Monadnock mountains is a deep valley, 

 cut down by Stony brook, and the place where the railroad passes from 

 Wilton to Greenfield. For two miles or more, the mica schists are well 

 exposed along the axis of the mountain ranges. In the saddle between 

 Pack Monadnock and Temple mountain the schists dip 30° N. 50° W. 

 On the west side and summit of Temple mountain the rock is mica 

 schist, with granitic beds, dipping 8°-io° W. At the south end of Kid- 

 der mountain in New Ipswich, which is of the same material with the 



