XII ILLUSTRATIONS. 



Pago. 

 XXIX. J, Basalt sUowiug characteristic texture in ordinary ligbt; B, Basalt showing 



obliteration of texture between crossed nicols 2if8 



XXX. A, Basalt showing in ordinary light a distinctly amygdaloidal texture; B, The same 

 basalt with its amygdaloidal texture obliterated when viewed between crossed 



nicols """ 



XXXI. J, Basalt atiected by calcification process; B, Basalt affected by calcification jirocess 



Tie wed between crossed nicols 292 



XXXII. A, Illustration of jierlitic parting in a fragment from a basaltic tufl'; B, Sickle- 

 shaped bodies in volcanic tuff 294 



XXXIII. A, Water-deposited sand ; B, Gradation in water-deposited volcanic sediment 296 



XXXIV. A, Contact product of granite ; B, Breociated matrix between ellii)8oid8 298 



XXXV. ^, Contact between granite and a metamorphosed sedimentary ; i3, Contact between 



n-ranite and a metamorphosed sedimentary viewed between crossed uicols 300 



XXXVI. A, A variety of spilosite with white spots ; B, A variety of spilosite with white spots 



viewed between crossed nicols 302 



XXXVII. A, Normal spilosite or spotted contact product ; B, Normal spilosite of somewhat 



different character - 304 



XXXVIII. ,1, Passage of spilosite into demosite; 5, Occurrence and alteration of bronzite in 



bronzite-norite 306 



XXXIX. ^, Biotite-granite viewed between crossed nicols; B, Jlica-diorite viewed between 



crossed nicols 308 



XL. ^, Quartz-mica-diorite-porpbyry ; B, Quartz-mica-diorite-porphyry viewed between 



crossed nicols ' 310 



XLI. A, Porphyritic poikilitic hornblende gabbro ; B, Poikilitic hornblende gabbro 312 



XLII. J, Moderately fine-grained hornblende gabbro showing parallel texture; J?, Mod- 

 erately fine-grained hornblende' gabbro showing parallel texture viewed between 



crossed nicols 314 



XLIII. A, Normal granular hornblende gabbro; B, Schistose hornblende gabbro viewed 



bet ween crossed nicols 316 



XLIV. J, Moderately fine-grained hornblende gabbro; S, bronzite-norite 318 



XLV. A, Bronzite-norite-porphyry ; B, Feldspathic wehrlite 320 



XLVI. A, Feldspathic wehrlite viewed between crossed nicols; B, Feldspathic wehrlite 322 



XLVII. Relations of magnetic beds to variation and dip 352 



XLVIII. Relations of magnetic beds to variation and dip 362 



XLIX. Geological map of the Felch Mountain Range 374 



L. Geological- map of a portion of the Crystal Falls district 450 



LI. Geological map of the Sturgeon River tongue , 458 



LII. Map of exposures in sec. 7 and portions of sees. 8, 17, and 18, T. 42 N., R. 28 W 474 



LIII. Schist conglomerate from dam of Sturgeon River 476 



Fig. 1. Reproduction of a portion of the geological map of the Upper Peninsula of Michigan, 



by William A. Burt, 1846 15 



2. Enlarged reproduction of a portion of a map of the Lake Superior land district, by Foster 



and Whitney 17 



3. Enlarged reprodxiction of a portion of a geological map of the Tjpper Peninsula of 



' Michigan, by Kominger, Brooks, and Pumpelly, 1873 18 



4. Granite-porphyry with inclusions of gueissoid granite 45 



5. Illustration of the effect on the topography of the differential erosion of basic dikes 



and granite '- 46 



6. Concentric cracks formed by the caving in of the Mansfield mine 65 



7. Sketch of the surface of the outcrop of an ellipsoidal basalt, showing the general char- 



acter of the ellipsoids and matrix — 112 



8. Sketch showing the concentration of the amygdaloidal cavities ou one side of an ellipsoid, 



this side probably representing the side nearest the surface of the flow 113 



9. Ellipsoids with sets of parallel lines cutting each other at an angle 114 



10. Reproduction of illustration of aa lava, after Dana 120 



11. Profile section illustrating results of diamond-drill work 177 



