114 BULLETIN OF THE 



No. 524 is a more compact rock of like character. Its groundmass is 

 kaoliuized and holds the quartz and feldspar alteration products. It 

 is filled with grains and masses of ferrite probably derived from horn- 

 blende. The feldspar is so decomposed that it cannot be told whether 

 it is plagioclase or orthoclase. Nos. 526 and 529 ai-e like No. 523, 

 while No. 530 is more allied to No. 524. 



No. 527 has a more coarsely crystalline, granitoid structure, showing 

 nnder the lens a reddish and grayish brown groundmass, holding elon- 

 gated bi-ownish-black hornblende crystals. In the thin section it is 

 seen to be composed of feldspar, magnetic iron, hornblende, and some 

 quartz. The feldspar is greatly altered, and is now composed of inter- 

 growths of feldspar and quartz, giving rise in it to a structure resem- 

 bling that of graphic granite, or much of that figured as belonging to 

 the Eozoon Canadense. The quartz is all secondary, and the hornblende 

 altered to reddish or yellowish brown ferruginous masses. 



No. 528 is a fine-grained granitoid trachyte (granite porphyry), but 

 in the thin section the feldspar is seen to be so altered and filled in with 

 secondary quartz, containing full and bubble-bearing fluid, and vapor 

 cavities, that the section resembles that obtained from some fragmental 

 rocks. No. 525 is a rock of similar character. 



Nos. 538, 539, 541, and 544 are good examples of some of the sand- 

 stones on the river below the melaphyr. No. 538 is seen in the section 

 to be composed of quartz and trachytic detritus. 



Below and at the base of the fells the dip remains the same as before, 

 N. 45° W. 10°, but above this locality the inclination varies, rising from 

 15° to 18° between the first and second falls. In some places a qua- 

 quaversal dip was seen. Some five falls exist in the river, and at the 

 last or vipper fall the melaph^-r was found. The dip of the sandstone 

 has now increased to some 20°, but still dips northwest, and the first 

 trappean flow is seen to overlie and greatly indurate and alter it. This 

 immediately underlying sandstone (537) is filled in with little reticulated 

 veins of calcite, a kaolin-like material, etc., and in general resembles the 

 baked sandstone found underlying the trap on the western side of Ke- 

 weenaw Point. Microscopically, it is seen to be composed of the debris 

 of the trachytes previous!}- described. This sandstone was seen within 

 three inches of the melaphyr, and although there may have been some 

 sliding motion between the two, as the contact was not seen, yet the 

 induration of the sandstone, its dip, and its relations to the melaphyr, 

 prove that it underlies the latter, which flowed over it. This, then, 

 with evidence obtained on the Douglas Houghton River, settles the 



