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MUSEUM OF COMrAIUTIVE ZOOLOGY. 



113 



could have lod Prof. Pumpcllj to state that an ash-bed was worked 

 there.* Specimen 814 is a good example of the end of a lava mass, 

 which still retains its original ropy and lluidal surface structure. This 

 came from the ash-bed at Copper Falls, a^d gives conclusive evidence 

 that it had never been water-worn. Tongues of the ash-bed were seen 

 extending down into its tuiderlying trap, while the overlying trap sends 

 tongues down into the ash-bed (Fig. 27). 



From their nature all the various lava flows are liable to be limited iu 

 any direction, either from their thinning out, the flow meeting obstruc- 

 tions, or from denudation since deposition, but before being buried under 

 conglomerate or the succeeding flow. They were evidently poured out 

 on a shore line, whose position probably varied relatively to the traps. 

 The intervals between the different flows seem to be brief in some cases, 

 while in others- considerable time must have elapsed. Figure 28 shows 

 the relation of the trap to the sandstone at one point in the Emerson 

 adit at Copper Falls, exhibiting the irregular surface of the latter before 

 the lava flow. 



The Sandstones and Conglomerates. 



As wo followed the Ilungarian River, a tributary of Torch Luke, np- 

 ward, starting from the low sandy pkins near the lake, the sandstone 

 was first observed forming high bluffs on both sides of the river, and 

 dipping N. 45° W. 10°. It occurs in coarse and fine layers often en- 

 closing pebbles. As the river is ascended the layers of pebbles were 

 seen to curve in various directions with an irregular dip, but which in 

 general inclined to the northwest. Some of the pebbles appeared to bo 

 of quartzite similar to that at Carp River, Marquette (522). The Hun- 

 garian Falls are formed by the river being precipitated over several 

 ledges of the sandstone and conglomerate. Several specimens were 

 taken, showing the different varieties of pebbles composing the con- 

 glomerate (523, 524, 525, 526, 527, 528, 529, 530). No. 523 is an old 

 trachyte composed of a reddish-brown groundmass, holding white kao- 

 linized feldspars, dark brown decomposed hornblende crystals, and a 

 little mica. It is closely allied to some of the modern rocks from the 

 Cordilleras. The groundmass is now kaolinized, forming a dirty-white 

 mass holding secondary quartz and feldspar, as well as long narrow 

 ferrite masses. These latter appear to have been formed from the horn- 

 blende fibres, so frequently seen in the allied rocks from the Cordilleras. 

 The groundmass has now through its alteration a spherulitic structure. 



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VOL. VII, — NO. 1. 



* Proc. Am. Acad., XIII. 283. 



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