August 21, 1896.] 



SCmNGE. 



217 



Can we not then conclude that the forcing 

 of acceptable food and drink into the phar- 

 ynx is not ' instinctive,' but is the result of 

 a series of satisfactory discoveries of the 

 young bird which lead up to the placing of 

 the food where it will bring about the stimu- 

 lation of the reflex center of the gullet and 

 the accomplishment of the final act of 

 swallowing— a series which is intelligently 

 adopted by the bird and improved by prac- 

 tice. 



It is perhaps well, before closing, to re- 

 vert to the peculiar habit of the bird in 

 snapping at falling drops. From the first, 

 the attention was markedly attracted by 

 flying insects and any small objects in mo- 

 tion seemed to have a peculiar charm. 

 From this fact I am inclined to think that 

 the seizing of drops was no more than the 

 striking at moving objects, though it is 

 possible that the adult habitually takes 

 water on the wing by seizing falling drops 

 of dew or rain. H. C. Bumpus. 



A NOBTREBN MIQHIOAN BA8ELEVEL. 

 Keweenaw Point and its southwestern 

 extension in northern Michigan is composed 

 of rocks of Keweenawan and Cambrian ages, 

 and exhibits three chief topographic fea- 

 tures. Beginning at the south is a broad area 

 of the so-called Eastern or Potsdam sand- 

 stone. This is in a horizontal position, 

 and rests unconformably upon the rocks to 

 the north and south. North of this area is 

 the main trap range of the Keweenawan, 

 which consists largely of basic lava flows, 

 but with lesser quantities of acidic lavas. 

 Interstratified with the lavas are numerous 

 layers of sandstone and conglomerate. The 

 majority of these are thin, but in the upper 

 parts of the series some of the conglomer- 

 ates are of considerable thickness. The 

 breadth of the main trap range varies from 

 about 4 miles to nearly 10 miles. In a gen- 

 eral way the traps and detritals strike north- 

 east and southwest, and dip to the north- 



west at angles varying from 25° to 55°. At 

 the southwestern part of the area consid- 

 ered, a wing of the trap range swings to the 

 north as the result of a fold. This area is 

 known as the Porcupine mountains. The 

 distance from the southwest part of the Por- 

 cupine mountains to the end of Keweenaw 

 Point is about 120 miles. To the northwest, 

 overlying conformably the main trap range, 

 is the upper division of the Keweenaw series, 

 which consists wholly of conglomerates and 

 sandstones. The dips on its southeastern 

 border average about 25°, but they become 

 less and less toward Lake Superior and at 

 the shore they do not average more than 8° 

 or 10°. 



For a full description of the Keweenaw 

 series see the Copper-bearing Rocks of Lake 

 Superior, by Roland D. Irving, Monograph 

 v., United States Geological Survey, and 

 in connection with the present description 

 see the maps of plates L, XVIL, and XIX. 



A recent visit to this area convinced me 

 that this district had been almost com- 

 pletely baseleveled. The two most advan- 

 tageous points found by me from which this 

 baseleveled area may be seen are, first, the 

 top of the hill occupied by a church in the 

 village of Rockland, and, second, the top 

 of the rockhouse of the Quincy mine, occu- 

 pying the highest ground above Hancock. 

 From the Rockland point, looking to the 

 northeast the main trap range appears to 

 be an almost level plain. To the southwest 

 the plain is nearly as level, but the Porcu- 

 pine mountains rise considerably above 

 this plain. The explanation of this monad- 

 nock is simple ; the core of the Porcupine 

 mountains is hard quartz-porphyry and 

 felsite, rocks more resistant than the inter- 

 stratified traps and detrital rocks of the 

 main trap range. From the Quincy rock- 

 house on a clear day the eye sweeps from 

 the Porcupine mountains on the southwest 

 to the end of Keweenaw Point, to the 

 northeast, that is, over the entire 120 



