CONTACT PHENOMENA 469 



accompanied by other rocks, in the south corner of Lyman and the west 

 part of Lisbon — probably a large faulted block — raised from below. 



These argillitic schists, like hornfels, seem to have been produced by 

 a widespread thermal agent, corresponding to igneous masses in contact 

 with earthy materials. Whether to say the igneous mass lay near 

 enough the surface to produce contact phenomena or to call the process 

 " regional metamorphism,"the result is the same. Materials of originally 

 diverse aspects have been reduced to a homogeneous paste. Hence in 

 mapping the distribution of this altered rock it must be borne in mind 

 that it may represent more than one original. 



Distribution of the Limestones 



It will now be possible to trace out the distribution of the fossiliferous 

 limestone series. The typical section indicates that besides limestones 

 there are dolomitic and slaty layers, which are often ferruginous. Be- 

 cause of the alterations, fossils may not be widespread or distinct very 

 far away. The best showing is the line of outcrop on the west side of 

 Blueberry mountain. All through Littleton and into the north corner 

 of Lisbon the limestone with distinct corals constantly shows itself, 

 usually in a valley. The depression may be followed to the height of 

 land back of Bald hill in Lisbon, where the continuity is obscured by a 

 thick blanket of till. Another valley succeeds with the same trend 

 toward Youngs pond, but no ledges are visible till half the ascent to the 

 next watershed has been reached. Here in abundance are the friable 

 shales, which continue to the top of the hill (called Knapp in the report), 

 where several large layers of limestone appear, carrying obscure corals 

 and fragments of small crinoids. I do not wish to assert an absolute 

 continuity of extent from the last seen coralline ledge in the north 

 corner of Lisbon, but the same formation with its fossils is present along 

 the line of strike. There is here a new association. On the west side 

 is a strong band of the auriferous conglomerate, and the course of this 

 band has been traced with exactness into Bath. The slates accompany 

 this conglomerate throughout, and seem to lie upon both sides of it. 

 The harder rock makes sharp bends, and the calcareous slates conform 

 to them. A good illustration is at what has been called the Dow ledge 

 on Smith brook in the south part of Lyman. The conglomerate lies at 

 the south foot of a high hill, and has been so bent as to form an acute 

 angle. Limestone bands adjoin it, displaying satisfactorily both the 

 planes of cleavage and of stratification, conforming to the harder strata. 

 The slates have a larger development farther south in Bath, where 

 both kinds of divisional planes are distinctly displayed. Many addi- 

 tional details might be given, but it would require the use of maps of a 

 large scale to render the delineation effective. 



LX— Bull. Geol. Soc, Am., Vol. 15, 1903 



