138 NINTH REPORT. 



ants of earlier geological conditions enter largely into the relief of the surface 

 of Michigan."' 



"Physical geography is the geology of the present, while one branch of 

 geology is the physical geography of the past."^ 



MICHIGAN GEOLOGICAL SURVEY. 



In the reports of the Michigan Geological Survey dealing with Monroe, 

 Sanilac, Huron and Bay counties the topics chiefly dealt with relate to climate, 

 configuration, elevations, surface and underground drainage, shore lines, 

 contours, elevation of the great lake basin and subordinately related sub- 

 jects. 



winchell's diagonal system. 



Dr. Alexander Winchell in 1873 read a paper before the American Asso- 

 ciation for the Advancement of Science entitled "The Diagonal System of 

 the Physical Features of Michigan. "^ 



"The actual topographical and hydrographical axes of Michigan and the 

 whole lake region, are the resultant of two forces — a glacial acting from the 

 N. E. and a stratigraphical acting along the lines of strike of the rock for- 

 mation. As a corollary we should find that where the rocky formations 

 are most consolidated, the resultant lies nearest the lines of the stratigraph- 

 ical force, and where the resultant approximates the line of the glacial force. 

 As a second corollary physical features determined by causes which have 

 obliterated the glacial and stratigraphical trends, do not, necessarily, ex- 

 press relations to either force. Of this kind are the small streams whose 

 courses over the diluvial beds have been determined by post-glacial erosions, 

 and river courses, like the St. Clair and Detroit, marked out across lacus- 

 trine or other post-glacial deposits which haA^e concealed the surface fea- 

 tures due to geological structure or glacial erosion."^ 



origin of the great lake basins. 



Michigan being a peninsular state the question is pertinent as to the causes 

 which produced the basins forming the adjacent great lakes. "It is to be 

 observed that concave tracts border the continents very generally. They 

 are connected with the descent from the continental shelf to the abysmal 

 basins and are unsymmetrical. Notable concavities are found in some of 

 the great valleys on the continental platforms. The basins of Lakes Su- 

 perior, Michigan and Huron are in part concave. When to the weakness 

 of the crust, as computed under ideal conditions, there is added the weak- 

 ness inherent in these concave and warped tracts, the conclusion seems im- 

 perative that while the crust is the pliant subjects of minor and nearly con- 

 stant warpings, such as are everywhere implied in the stratigraphic series, 

 it is wholly incompetent to be the medium of those great deformations which 

 occur at long intervals and mark off the great eras of geologic history."* 

 The Lake Superior basin as thus stated is an early crustal warping which 

 antedates Paleozoic time. The basins of Lake Michigan and Huron occupy 

 lateral parts of a considerable earth concavity existant during early Paleo- 



1 Bay county, W. F. Cooper, Ann. Rep. of the Mich. Geol. Surv., 1905, p. 355. 



2 A. C. Lane, Mich. Geol. Surv., Vol. VII, Pt. 2, p. 31. 



3 W. H. Sherzer, Monroe Co., Geol. Surv. of Mich., Vol. VII, part I, p. 118. 



4 Tackabury's Atlas, A. Winchell, 1883. 



5 Chamberlin & Salisbury, Geology, Volume I, pp. 558-562, 1904. 



