Ancient Lake Beaches

During the past two weeks. Prof. J. W. Spencer, 8 Car.adian geologist, and Dr. Wooldridge, of Ann Arbor, have been jointly engaged in sn investigation of ancient lake beaohes existing in ihis región. It may be remembered that last July The Register published anarticleby Dr. Wooldridge describing the gravel beds of Ann Arbor in their relution to the clay hills and uplands surrounding, and setting forth the conclusión that the Ann Arbor gravel beds are an ancient delta formed of sediment forced by the Hurón river into a bay oecupying the present site of Ann Arbor. More recently Dr. Wooldridge has disoovered unmistakable evidence that at least two ancient water margina pased through the site of Ann Arbor, the upper and older of which coincides with the height of the campus, while the other mark9 a pause in the retreat of the water at a level about 30 feet lower. Using these facts for a pointer, Prof. Spencer and Dr. W. have now been gaged in making an exploration of the country, aided by an engineer's level, I through an extent of 35 miles or more, extending from Southwest to northest on both sides of Ann Arbor, and to the southward. In this región they have áiscoveredancier.t beachesin many places, sometimes of the most marked and typical character, and have determined their relative heights. What has from the settlement of the country been known as the "old lake ridge," has beea recognized as an ancient beach as long as it has been known. This passes about four miles east of Ypsilanti at a level about 85 feet lower than the campus in Ann Arbor, and it was while engaged in tracine this beach toward the north that Prof. Spencer visited Ann Arbor and had his attention called to the upper beaches existing here. The exploration made by him jointly with Dr. Wooldridge above the level of this beach, has resulted in the discovery of an important and well marked beach, at a level 40 feet higher tban the old lake ridge that hag been long supposed to mark the highest level at which the waters ever stood in this región, and has ahown that at the epoch of these upper beaches there was in this reeion a succession of deeply indenting bays, and an archipelago of slands which have greatly complicated and obscured the traces of these ancient water margins which now remain. These are facts of much scientific interest, and Dr. Wooldridge has been for some time in communication with the U. S. Geological survey in regard to them.