236 STRATIGRAPHICAL GEOLOGY. 



may be obtained, which might answer for tombstones or for platforms, but no attempt 

 has yet been made to quarry them. Higher up the mountain we discovered a very 

 singular breccia, made up of the large broken fragments of the argillaceous slate 

 rocks, mixed confusedly with the granite which closely invests them. This breccia 

 was evidently formed by the eruption of granite through a thick bed of argillaceous 

 slate rocks, the strata having been broken into fragments of a rhomboidal form, and 

 into pieces which vary from a few inches to a yard or more square. The fragments lay 

 in every imaginable position, just as if they were swept up by a thick, pasty mass of 

 semi-fluid granite, which indurated around them by cooling. Some of the masses were 

 rendered scoriaceous, and resemble vesicular trap rock, but generally they do not ap- 

 pear to have been much altered by heat. The granite contains no mica, but is com- 

 posed principally of feldspar, with a little quartz. There are no rounded or waterworn 

 pebbles in the breccia ; hence it cannot be considered as a conglomerate of aqueous 

 deposition. This locality proves most incontestibly * * * ^^^t the eruption of 

 the granite rock of this region took place immediately after the deposition of the roof- 

 ing slate. * * * On reaching the summit, the rocks were found to consist of a 

 very hard breccia, composed of the same kind of granite before described, containing 

 small fragments of slate rarely more than an inch in diameter.* 



The accompanying heliotype of Mt. Pequawket will show better than 

 words the relations of the several rocks to each other. The view was 

 taken from a small hill east of the McMillan house, and south of the 

 Portland & Ogdensburg Railroad depot in North Conway. The lowest 

 rock receiving a color is the Conway granite, which also occupies all the 

 foreground not otherwise designated. About three hundred feet of the 

 lower part of the mountain are entirely composed of this granite. It has 

 been found at about the same elevation above the sea on three sides of 

 the mountain, — hence the conclusion naturally suggested is, that its sur- 

 face is a nearly horizontal floor. The next strip is likewise nearly hori- 

 zontal, thickening at the western side towards Bartlett. This is the 

 Albany granite, perhaps fifty feet thick, on Section VIII, No. 6. This 

 has been seen at several localities on the south side; and, on the path 

 usually taken in the ascent of the mountain, it is thought to be from one 

 hundred and fifty to two hundred feet thick, and still thicker on the slope 

 towards Saco river in Bartlett. The position of the slate is indicated by 

 the small patch of color overlying the narrow belt of Albany granite. 

 The upper part of the mountain consists of a breccia, in which the fcld- 

 spathic paste may vary from three to ninety-nine per cent, of the mass, 



* Final Report, p. 8i. 



