Douglass Houghton. — ,1. Winchcll. 135 
Grand Traverse bays "are without doubt, a continuation of the 
line of bearing of the great limestone formation of Wisconsin." 
On the whole, however, Dr. Houghton reveals in this first 
glance at the general geology of the Lower Peninsula the tact 
and sagacity of a skilled observer. This report is accompanied 
by those of the various assistants. 
Tlie report of observations made by Dr. Houghton in 1839, 
dated February 3, 1840, is devoted to the Northern Peninsula. 
This and that of the following year, dated February 1, 1841, 
are the two most important and original contributions made 
by Dr. Houghton to geological science. In these reports he 
describes the rocks of the Upper Peninsula under the follow- 
ing divisions: 1. Primary Rocks, 2. Trap Rocks, 3. Mcta- 
morphic Rocks, 4. Conglomerate, 5. Mixed Conglomerate and 
Sandstone, 6. Lower or red Sandrock and Shale, 7. Upper or 
Gray Sandstone, 8. Sandy Limerock. The Primary Rocks 
consist chiefly of granite, syenite and syenitic granite. The 
extended range of Trap Rocks flanking the Primary rocks on 
the north or northwest (relative positions being reversed on 
the north shore — hence, he says, proving the basin of the lake 
synclinal) are themselves flanked on the north by amygdaloids 
which in part, result from the intense alteration of sedimentary 
rocks next in order. From the masses of greenstones proceed 
dykes (so called) which intersect the newer formations in 
planes conformable with their bedding. The writer gives a 
careful and particular description of the true veins which in- 
tersect the dykes, the amygdaloid and the sedimentary rocks,' 
but, like the dykes, they coniform to the bedding of the amyg- 
daloid and the sandstone. These veins, he says contain native 
copper." 
The Metamorphic rocks consist of talcose, mica and clay 
slates, slaty hornblende rock and quartz rock. These are the 
rocks claimed by ICmmons as representing the Taconic system 
in ^[ichigan. To these must be added the argillites first 
reported as included in the "Lower Sandstone and Shales." 
^Besides the descriptions embraced in these reports, Dr. Houghton 
presented a careful summary touching mpt.alliterous veins, before the 
''Association of American (jeologists" at Philadelphia, in 1S41. (See 
Transactions, pp. .S.5-;iS. See also, Amor. Jour. Sci. 
•^A statement which aroused a discussion in the meeting of 1S43. 
Amrr. Juur. Sci. XLV. p. IHO, 1843.) A report was made on the subject 
in 1844 iAmer. Jour. Sci. xlvii, 132, 1S44). 
