water tastes and smells of hydrogen sulphide and is depositing sulphur. Similar springs with mounds of tufa are found to the south, upon lands of Mrs. Adeline Q. Navarre and Joseph Asam.

A large sulphur spring occurs upon the place of Peter Cushino, Otter Creek, near the Sharkey well just described. This has an elliptical basin 45 by 90 feet, with a 10 foot margin richly covered with Chara. The stream from the spring is not rapid, is 2 feet broad and 10 inches deep. A similar but much larger spring occurs in the Erie marsh near Vienna, N. E. 4, Sec. 22. It is reached by boat by punting one-half mile through an artificial channel. At a

distance the site of the spring is marked by a spot of the most livid green contrasting strangely with the dark waters of the marsh. The general form of the spring is circular as shown in Fig. 8 and its diameter is about 160 feet. The bottom is funnel-shaped, a marginal strip of 25 to 40 feet shelving off slowly and then making a sudden drop. The bottom where visible through the clear water is covered with a mat of Chara, encrusted with a deposit of sulphur. The sounding line struck bottom at 30 to 33 feet, although it is quite probable that fissures occur leading to greater depths. The outlet from the spring is a small sized river having considerable velocity, a breadth of 33 feet and a depth of one to two feet. The current is so swift that there is some difficulty experienced in entering the

spring with a boat. The channel soon becomes broader and proportionately more shallow, and over the bottom of it much sulphur has been deposited. Fragments of tufa are found about the margin of the spring showing that the water is probably rich in calcium carbonate. It is very probable that these springs and flowing wells are fed by the water which enters the rocks in the western part of the county.

§ 11. Marl.

No extensive beds of this substance, for which the Portland cement industry has created a demand, are known to occur in the county. The largest deposit known occurs upon the property of Joseph Asam, claim 422, north of Plaisance Creek. Over an area of 6 to 8 acres there is a layer of black spongy muck containing many dead shells of Helix. Beneath this is found a bed of marl varying in thickness from one to three feet. The marl is so free from grit that, after washing, it has been found to produce a good polishing powder for gold, silver, nickel, brass etc. It was boxed and sold for this purpose some twelve years ago under the name Paragon Polishing Powder, being prepared by the La Plaisance Manufacturing Co. The marl contains some shells but appears to have been in the main precipitated from the water of a small lake charged with lime carbonate. Such a deposit may now be seen in process of formation over the bottoms of the series of lakes through which the Huron River flows in Washtenaw county. Upon claim 161, about one mile west of the Asam deposit at the place of Eli P. Duval, there is said to be a black deposit with white clay. The latter is undoubtedly marl and a similar reference to a 10 inch layer of "whitish dirt" was obtained at W. J. Kelley's, claim 520, South Otter Creek, where it is overlain by 2 feet of yellow sand and one foot of black sand. Beneath the sand layer is one foot of yellowish-white clay, 1 inches of gravel and then common clay to the rock. Judging from these deposits we have here a former lake site. At the cranberry marsh belonging to Clayton Everett, of Toledo (S. E. 4, Sec. 24, Summerfield, see p. 157), more or less marl occurs, but the maximum thickness is said to be but 6 to 8 inches. It is quite probable that thicker deposits occur towards the center of the marsh, possibly of.considerable extent. In his early report Hubbard reported marl as occurring on Sec. 7 of Exeter and Sec. 9 of Ash townships.* A very extensive marsh occurs in Sec. 9 of London and probably contains marl be*Second Annual Report of State Geologist, 1839, H. R. No. 23, p. 110.

neath the surface. It might be possible to dredge out here both marl and a suitable variety of clay for Portland cement. The clay would be found beneath the marl if both occur. Such use is the main one for this loose variety of lime carbonate. Its value as a fertilizer and for neutralizing the acidity of muck has been referred to in the previous chapter, p. 172. In the early days it was sometimes converted into lime by heaping it up into a pile and keeping a wood fire going around and over it until the carbon dioxide gas was driven off sufficiently.

§ 12. Salt.

Springs along the Saline River furnished a weak brine for the use of the Indians and pioneers, but the main one was in Washtenaw county (T. 4 S., R. 5 E., Sec. 12). In 1823 this spring was described as being 16 feet deep, set about with a picket of logs from which the surface water was excluded by means of an embankment. Salt was manufactured here on a small scale, an analysis showing 113.8 grains of salt in 100 cubic inches of the water.* Dr. A. Winchell, in his report of 1860 (p. 59) refers to a salt spring in Ida township, 4 miles south of the Raisinville quarries. No such surface springs could be located by the present survey, probably owing to the diminished flow from wells and springs. In Berlin township, S. E. 4, N. W. 1, Sec. 15, at the place of A. Bondie, the well water is reported as being occasionally salty to the taste. In Lenawee county, north of Deerfield, this phenomenon is more common. Such indications are of interest now only as they suggest the presence of more extensive saline deposits beneath the surface. Undoubtedly the waters obtained from the deep wells of the county are highly charged with salt but no study has been made of them. In but one of these deep wells was there recognized a stratum of solid rock salt (halite) and in this case the report lacks verification. According to a newspaper item, at a depth of about 1,200 feet, a 12 foot stratum of salt was penetrated in the Frey well, near South Rockwood (N. E. 4, N. E. 4, Sec. 33, T. 5 S., R. 10 E). This occurrence was not to be expected since the records of the six wells at the Church and Company's plant north of Trenton seem to indicate that the St. Clair and Detroit River beds of salt give out between the most northern and most southerly located wells of their group. Well No. 6 gives a stratum of 33 feet while Nos. 4 and 1 and 3 lying in this order to the east

*First Annual Report of the State Geologist, 1838, H. R. No. 14, p. 28.

give 30 feet, 26 feet and 25 feet respectively. Well No. 2 lies about 300 feet south of the above and shows but 2 feet of salt while in No. 5, some 800 feet south of the northern row, only a brine was secured with no solid salt. If the rumor in regard to the Rockwood well be founded in fact it will be necessary to assume that minor salt beds were deposited south of the main series after the inland sea had begun to break up into separate bodies of water (Chapter III, § 5).

CHAPTER IX.

§ 1.

MINERALS OF MONROE COUNTY.

Introduction.

In this chapter it is desired to describe in simple language the native minerals so that they may be readily identified by those interested, even if they possess no previous scientific knowledge or training. After a mineral has been recognized the question of its formation and source becomes of more or less interest and importance, so that the history of the various mineral deposits will be briefly presented. There are excluded from the list all those minerals which were formed to the north and east and which were transported to the region under study by ice or other agency. This chapter will then be of little service in identifying the constituents of the drift boulders strewn over the surface or embedded in the soil. Almost any mineral known may occur in them. It will treat only of those mineral substances which were formed within the limits of the county, some of which are at the surface but most of which are contained in the rock strata and are now met with in the quarries and well drillings. A mineral has been defined as a natural, homogeneous, inorganic substance; but this definition, simple as it is, requires some explanation. It must have been formed entirely through the operation of natural agencies without the intervention of man. The substance itself must have practically the same chemical composition throughout, although it may have mixed with it more or less impurity. It must be of inorganic origin entirely, or if derived from plant or animal originally, its organic structure must. have been practically destroyed.

This is the most common and widely distributed mineral of the quarries. It is found filling seams and crevices in the limestones and dolomites and forming beautiful sparry lining to fissures and