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MUSEUM OF COMrAKATIVE ZOOLOGY. 



215 



granite in the course of the trail, whicli is just at the foot of the pres- 

 ent terminus of the Southwest Slide. At both localities the rock is of 

 tiie coarse gray variety that is exposed at the third and fourth falls, 

 and is destitute of glacial markings. The surffice is honeycombed by 

 decay, which, at the lower station, lias gone so far that it was there 

 impossible to break out, with a heavy hammer, specimens which at all 

 approached a soiind condition. 



The only rock in place to be seen upon the Southwest Slide occurs 

 two thirds the way up from its foot, at an elevation of about 3,500 

 feet. It is a fine-grained, dark gray granite, approaching in appearance 

 some of the inclusions that are found in the basin, and well adapted to 

 resist decomposition. It lies, as at the stations below, in concentric 

 sheets,* which have here an inclination of about 30°, a.nd is smooth, 

 hard, and free from all indications of decay ; but not a scratch or 

 other sign of glaciation appears upon it. It is a small area, only sev- 

 enty-five feet along the slope, and perhaps a third as wide, and dis- 

 appears above, below, and at the sides, under the debris of the slide, 

 beyond the slanting face of which the ledge scarcely projects. If it w^as 

 first uncovered, in recent times, hj the descent of the avalanche of 181G, 

 as from the surroundings seems not improbable, the absence here of 

 grooves and strite is significant as respects the glaciation of the higher 

 parts of the mountain. 



If evidence of glaciation upon the sunmiits of Ktaadn exists, it must 

 be other tlian that to be derived from smoothed and striated surfaces. 

 It will bo maintained by many tliat such evidence is sup[)lied by the 

 flat tops of the Table Land, and of several of the spurs, and by the well- 

 rounded northern summits and faces. To this it may be objected that 

 table~to])ped mountains are not wanting in regions where neither drift 

 nor other indications of glaciation have been recoiJ:nized. 



The state- 



h 



meut, however, \s open to the rejoinder that, in such cases, the shape 

 may be rationally accounted for by obvious peculiarities of structure, as 

 is the typical instance of Table Mountain, near the Cape of Good Hope, 

 which is a mass of granite capped by horizontal beds of sandstone. 

 The prevalence of steep faces upon the sides of Ktaadn, as already re- 



* My ob.servtitioii of Maine ^n-aiiitos in i,^ciu'Ta!, and ospceially at Mt. Ktaadn, 

 foi'ccs inc to tlio conclusion that th(; conccnfric laniinalioii of ^n-aiiito is due to causes 

 conitecicd witli tbc orii^dnal structure of the rock, and not, as has hoeu uiaintained 

 by rrof(!ssors SJialcr and Jiunt, to superficial variations of toni})erature during tlio 

 changes of the s(!iisoiis. It would seem, then, to be putting tonus in llu-ir hii^ncai 

 oi'ih'r to speak of the coufornuly of preseul surfaces to the inclination of the "•riinitc 

 sheets, ratlier than of the lanunation as confoi'inablc with superficial features. 



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