"Winchell.] "'J [March 5, 



cal position, we find all these formations lying beneath the Mississippi 

 limestones and above the Genesee shale. 



The synchronism of the Waverly and Gritstone series of Ohio, -with 

 the Portage and Chemung of New York, has not only long been 

 asserted — at least at invervals — by Professor Hall, but has been generally 

 assented to by others, who have had occasion to consider the subject, or 

 have felt disposed to defer to competent authority. The controversy 

 which has existed has been rather in reference to the systemic position 

 of the two, as the citations which I have already made from the history 

 of the controversy sufficiently indicate. The Waverly series has gene- 

 rally been regarded of late years, as extending down to the Black Shale ; 

 and the denial of the parallelism of this series with the Chemung and 

 Portage has appeared to leave no space for the existence of the latter 

 groups in Ohio. There is, as Professor Hall has frequently asserted, an 

 improbability that a groui) more than a thousand feet thick in western 

 New York, should have completely thinned out before reaching the 

 meridian of Cleveland or the peninsula of Michigan. There are some 

 facts in my possession, however, bearing upon this subject, which I have 

 never yet had the opportunity to bring into jDrominent notice. 



In my Report on the lower peninsula of Michigan I described a series 

 of argillaceous strata^^^ underneath the Marshall sandstones, and ex- 

 tending to the Hamilton limestones. The Genesee Shale constitutes the 

 lower portion of this group — being structurally a portion of it. In my 

 Report I assign but 210 feet of thickness to this group, as this was all 

 that I had actually measured at outcrops ; but borings subsequently 

 executed in various parts of the State, show that the group actually pos- 

 sesses a thickness of 500 to 600 feet. '"^ This mass occupies the place of the 

 Portage and Chemung strata. In the southern portion of the State it 

 is quite purely argillaceous, passing vertically at intervals into mica- 

 ceous arenaceous shales, or even calcareo-arenaceous flags ; but in its 

 northern outcrops, we find compact flagstones frequently intercalated in 

 the series, giving it a physical approximation to the New York strata, 

 whose stratigraphical position it usurps. Moreover, in Grand Traverse 

 Bay, we discover, not far above the Genesee Shale, a mass of .green are- 

 naceous shales which apparently answer to the Cashaqua Shale of the 

 Portage group. 



We have in this series all that is requisite to answer the demands of 

 the Portage and Chemung groups. The thickness is, indeed, conside- 

 rably reduced ; but it must be remembered that all the other New York 

 groups traced into Michigan exhibit even a greater attenuation than this 

 parallel would imply. '"^ 



I" I embraced in this group I-l feet of gritstones, wliich I subsequently removed, on studying 

 tbeir paleontology. (Amer. Jour- Sci. [2] xxxiii., 352. 



"» I have several times published these later determinations, but Dr. Hunt continues to quote 

 from my Report of 1S61, (Amer. Jour. Sci. and Arts, xlvi., 357,) having evidently overlooked my 

 later announcement. (See, for instance, "The Grand Traverse Region," (1866) p. 52.) 



109 Dr. Hunt thinks the Salina Strata will yet be found to attain a greater thickness in Michigan 

 than thai assigned to them in my Report of 1S61, (Amer. Jour. Sci. and Arts, xlvi., p. 351).) The 

 facts announced by him would certainly ju.stify such an expectation; but I embrace the opportu- 

 nity to state that though bored through in several places since thedate of my Report, the thickness 

 has not been found materially greater than stated in 1S61. 



