nial Report, published in 1861, contained the results of this field. work* (pp. 58-68). The light colored, argillaceous limestones of the Davis quarry, west of Ida, were identified as those of the Onondaga Salt Group, on account of the gypsum present. The same beds were believed to appear at Ottawa Lake and to be struck in the deeper portions of the Plum Creek quarries, and the suggestion is made that gypsum be sought for at these localities, as well as in the gorges of Otter Creek. The thickness of the Onondaga in Monroe county is given as 24 feet; the first 10 feet of which is a chocolate colored limestone, the remainder fine ash colored, argillaceous limestones, with acicular crystals (p. 140). The Upper Helderberg is given a thickness of 60 feet in the county, and was made to include the brecciated dolomites of Stony Point and Point aux Peaux, the two beds of oölite, the Sylvania sandstone and the purer limestones on the Macon.

The work of the survey was interrupted by the War of the Rebellion and not resumed again until 1869, with Dr. Winchell again State Geologist for two years. Materials for a valuable volume were prepared but were never published in the manner intended. Some of it, however, appeared in Walling's Atlas of Michigan and was subsequently put out (1873), as a small volume bearing the title "Michigan." The occurrence of the Lower Helderberg (Waterlime) had been announced in 1870. This formation was recognized in the quarries in the eastern part of the county and considered to attain a thickness of 60 feet. The geological map which accompanies the volume gives a narrow strip of Lower Helderberg, three to four miles wide, following the shore of Lake Erie, with a broad belt of Corniferous to the west and embracing nearly the entire county. Small islands of Salina, with marginal strips of Lower Helderberg, are represented at Ida and Ottawa Lake, and apparently also at Monroe and Brest. The Little Traverse appears as a narrow belt, with the general strike and position which the Corniferous ("Dundee") is now known to possess, while the Huron shale covers the remaining northwest corner of the county. This corner is just grazed by the Marshall sandstone. The formations which overlie the Lower Helderberg are thus seen to be displaced to the east. The following "generalized section" was intended to include all the Monroe county beds, except*1861. First biennial report of the progress of the G. S. of M. Embracing observations on the Geology, Zoology and Botany of the Lower Peninsula. Made to the Governor Dec. 31, 1860.

ing the Little Traverse and Huron, which are not here known in outcrop.

IV. Brown bituminous limestones, seen in most of the quarries of Monroe county; also in Presque Isle and Emmet counties, 75 feet. III. Arenaceous limestone, sometimes resolving itself into beds of friable sandstone and incoherent sand. Monroe county; also Crawford's quarry, 4 feet.

II. Oölitic limestone, as in Bedford and Raisinville, Monroe county, 25 feet.

I. Brecciated limestone, sometimes concretionary, 50 feet. § 14. Rominger survey.

Dr. Carl Rominger began his examination of the rocks of our southern peninsula in 1873, making a detailed, careful study of all the beds and their fossil contents. The results of his three years' personal work are recorded in Vol. III, Geological Survey of Michigan, 1876. That portion of the report which deals with the rocks of Monroe, and the adjacent portions of Wayne county is recorded on pages 25 to 37. The limestones of this region he described under the single heading "Helderberg group," but recognizes an upper and lower division, equivalent to the Upper and Lower Helderberg respectively. The lithological characters of the beds are accurately noted and simple analyses given of the more important, some of which will be incorporated into this report. The Sylvania sandstone he gives a thickness of but 8 to 10 feet and, following the earlier reports of the Ohio Survey, regards it as probably the equivalent of the Oriskany sandstone, of New York (p. 29). The oölite of Plum Creek and Little Lake he regards as the geological equivalent of the sandstone (p. 28), being misled by the beds of mottled dolomite which underlie each, but which are actually many feet apart. A still more serious error was made in bringing the base of the Upper Helderberg down to the top of the Sylvania sandstone, based upon the lower percentage of magnesia in these beds. The quarries of Ottawa Lake, Little Sink, Lulu, Ida, Raisinville, Woolmith and Flat Rock are all in beds above the Sylvania and still contain practically enough magnesia for normal dolomite. Both lithologically and palæontologically these beds immediately above the Sylvania must be connected with those beneath.*

Dr. Rominger does not admit the occurrence of the Hamilton *See Geological Survey Ohio, Vol. VII, p. 17.

(Traverse) in this portion of the State (p. 38), believing that from the thickness of 500 feet near Alpena, it thins out completely before reaching the southern boundary. Reasons will be given later for thinking that the Traverse is well represented beneath its heavy mantle of drift in the northwest corner of the county. Upon the geological map that accompanies Vol. III the structure of Monroe county is much simplified by uniting the Upper and Lower Helderberg into one division, not representing the Sylvania and imposing the St. Clair shale directly upon the Upper Helderberg.

§ 15. Work of present survey.

While searching for natural gas in the early fall of 1887 at the plant of the Eureka Iron and Steel Works, in Wyandotte, the drill from 730 to 1,235 feet passed through a series of layers of pure rock salt. The newspaper announcements of this incidental discovery caught the eye of interested parties in the East and experts were soon upon the ground. The remarkably pure beds of limestone, two miles distant, combined with unusual shipping facilities, made the region almost an ideal one for the manufacture of soda ash and caustic soda. Establishment after establishment has sprung up along the Detroit River, representing millions of outside capital and employing an army of workmen. Other extensive plants are seeking locations and are inquiring for high grade limestone. The rapid development of the Portland cement and beet sugar industries in our State has greatly increased the demand for natural products.

The records of the Wyandotte well above mentioned and of a well at Monroe down into the Trenton which were collected during the administrations of State Geologists C. E. Wright and M. E. Wadsworth were printed in Part II. of Vol. V of the State Reports. There is also a geological map of the lower peninsula in this volume, which shows the course of the Sylvania sandstone, and the terms applied to the various members of the rock series which we use. During this time the records of the Dundee and other wells were acquired by the State Survey, and by the spring of 1896 it was decided to arrange. for a thorough survey of this most promising corner of the State and to render available at once, by means of a bulletin, what could be learned of its resources. The work was begun under Dr. Lucius L. Hubbard and after his resignation, continued and completed under the present organization. July and August, 1896, and August, 1897, were devoted to the field work by the writer, assisted the first season

by Mr. W. D. Cramer and later by Messrs. R. R. Putnam and De Forest Ross. For purposes of comparison, a careful study was first made of the extensive Sibley quarry, north of Trenton, and of the smaller quarries and outcrops about the Detroit River. Within the county every known natural and artificial exposure of the rocks was visited, the strata studied, samples and fossils collected and each quarry platted. From convenient centers, a study was made of the soils and their distribution and much detailed information gathered in regard to the depth and character of the rocks, the nature of the drift deposits, water supply, timber and crops, indications of oil, gas, etc. From Ottawa Lake a side excursion was made into Ohio to examine the exposures of the Sylvania sandstone and adjacent strata. The delay in the publication of the bulletin necessitated a final general survey of the county, in order to bring the information to date and nearly two weeks in September, 1899, were devoted to this purpose. The Raisin was found to be exceptionally low and a favorable opportunity was afforded for studying the strata over which it flows. As to the results secured and conclusions reached the body of the report must be allowed to speak.

§ 16. Acknowledgments.

It is a pleasure to acknowledge here the uniformly courteous treatment received from the farming population of the county. Much of this report has been rendered possible only through information received from them. Only in a few cases, where they feared that they were being victimized by some new scheme, was information withheld or grudgingly given. It is hoped by getting the benefit of generalizations, based on their combined knowledge, that they may be, in part, at least, repaid. The numerous well drillers, with but a single exception, have given their valuable information, the result of years of labor and the expenditure of much money, freely and gladly. Especial acknowledgment is due Mr. John Strong, of South Rockwood, and his driller Mr. H. S. Dalton, for information and series of samples of the Newport well. To Church & Co., through their courteous manager Mr. K. J. Sundstrom, the survey is very especially indebted for maps, charts, negatives, analyses, and valuable information pertaining to the region, with every facility for the study of their extensive Sibley quarry. The same generous treatment was accorded by Mr. G. F. Smith, at the time president of the Michigan Stone & Supply Co., and by the offi

cers of the Monroe Stone Co. We are indebted for our topographic base very largely to the county atlas published by Geo. A. Ogle and Co., of Chicago in 1896, Finally, to Mr. Ezra Lockwood and family, of Summerfield township, grateful acknowledgment is made for generous hospitality, conveyances and valuable information, the result of many years' intelligent observation and experimentation in the prairie region.

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