476 C. H. HITCHCOCK — AMMONOOSUC DISTRICT, NEW HAMPSHIRE 



minds were preoccupied with different theories for their origin. We 

 had accepted the view of the presence of older crystallines, and the phe- 

 nomena seen along the stream were explicable on that theory. These 

 diorites are more abundant to the north of the section near Streeter 

 pond, but have not been seen farther south because of an extensive cov- 

 ering of the rocks by drift.* 



LlSBON-SwiFTWATER COMPLEX 



In the state report the local name " Lisbon " was applied to the green 

 schists, and '" Swiftwater " to an indefinite group of mica schists, slates, 

 and conglomerates, both making parts of one whole. For convenience, 

 in description the double name may be employed, it being understood 

 that the fossils found in the limestone will give character to the whole, 

 though they have not yet been seen in the southern portion of the area. 



More particularly the Lisbon rocks are green chloritic schists and 

 sandstones, igneous diorites, granites, and protogenes, at first thought 

 to be stratified ; hydromica schists, quartzites, limestones, conglomer- 

 ates, etc. The Swiftwater rocks are mica schists, quartzites, hornblende 

 schists, slates, argillitic and sericite schists, and obscure conglomerates. 

 These two groups were separated from each other on the published 

 map, but further explorations indicate that none of these rocks are re- 

 stricted to any particular horizon. The last named series seems to 

 underlie the other. At the northern end of the district the Coos group 

 was distinguished from the other, but our later studies would indicate 

 that these quartzites and mica schists, with others of an argillitic char- 

 acter at this locality, belong to the same general Paleozoic Lisbon-Swift- 

 water complex. The greater breadth of the southern part of the complex 

 may be due to duplication by folding. 



The quartzites of Littleton seem to be silicified mica schists and 

 merge into the strata connected with the limestones on Manns hill. 

 The formation of the broad valley in which the village of Littleton is 

 situated has removed or concealed the ledges by alluvial deposits, but 

 their continuation to the south is evident on Walker hill, in Lisbon. 

 A characteristic whetstone mica schist is traceable from South Littleton 

 across to the well known quarry in the north part of Lisbon. All these 

 rocks underlie the coralline limestone. 



* Three varieties of the rocks from this section were sent to Professor G. P. Merrill for deter- 

 mination, who turned them over to Mr W. C. Phalen, who sends the following descriptions : 



Number 2 already quoted, page 4G7. 



"Number 3 is practically the same as number 2, so far as constituents go. There is a good de- 

 velopment of plagioclase, and for that reason the rock might be classed as diorite." (Mentioned 

 on page 470.) 



" Number 4, principally fine grained aggregate of amphibole and feldspar, and may appropri- 

 ately be called Lamprophyre if in dike form or a diorite if in massive form." 



