THE

AMERICAN

JOURNAL OF SCIENCE AND
AND ARTS.

[SECOND SERIES.]

ART. XXXII.—On the Fluctuations of the Water Level at Green Bay, Wisconsin; by CHAS. WHITTLESEY, of Cleveland, Ohio.

THE town of Green Bay is situated at the mouth of the Fox (or Neenah) river. As far up the river as "Des Peres," or about five miles, the water is dead and deep enough for navigation by sail vessels. The first rapid is at Des Peres, the seat of the earliest French mission on the Fox river, taking its name from the Jesuit fathers, of whom relics yet remain. Here a dam and lock have been built as part of the improvement of the river.

Movements of the waters at the mouth and along the still water portion of the channel are so frequent and so marked as to attract the attention of travellers and residents from the days of the Jesuits to our own. The current is seen flowing rapidly up stream as far as the rapids almost every day, and sometimes more than once or twice. With the influx is a rise sometimes very small, at others reaching one and even two feet, as the following tables show.

Notwithstanding the curiosity excited by this series of movements, very few measurements have been made. The early numbers of this Journal contain, I believe, all the observations heretofore made, but I have not the advantage of referring to them. Those which I now present are by no means complete, but may be of some value in discussing the question of lunar influence.

SECOND SERIES, VOL. XXVII, No. 81.-MAY, 1859.

In the month of August, 1858, at my request, D. UNDERWOOD, Esq., cheerfully consented to make hourly observations so far as it could be done consistently with his occupations. Mr. Underwood is the observer at Green Bay for the Smithsonian Institution at Washington: a capable and faithful person, having a strong inclination for all subjects connected with natural science. The bay which has given its name to the town, is on an arm of Lake Michigan, about 120 miles in length, and its greatest width about 20 miles. It opens into the lake not so much by direct channels as by side ones among islands that lie across the mouth, which is about 25 miles in width. In general form it resembles the half-fledged wing of a bird attached to its body by its side and at the largest end. The general direction of its axis or middle line is northeast by north, making an acute angle with the coast line of Lake Michigan. A narrow peninsula coming to a point at the "Port-des-Morts," lies between the bay and the lake, rising from 100 to 200 feet above the water level. The western shore of the bay is low and swampy; winds that blow across the bay from the northwest, therefore, act more powerfully on its waters, locally considered, than those from the opposite quarter over the bluffs of the eastern shore. At Green Bay and Fort Howard the shore lines approach to a point.

From Mr. Underwood's register I have to a considerable extent condensed the readings so as to express them in substance, in the form of curves. At the broken or dotted portions the observations are wanting. We assumed an arbitrary line or plane of reference intended to be above the floods of the year 1858, and called this zero.

Constructing a water-gauge, marked to half inches, it was nailed to a pile at the south side of the dock of Day & Brothers, its zero corresponding with the assumed line, the figures reading downwards. The readings were made hourly during the day, but were necessarily deficient for most of the nights.

By means of the tables and of the diagram [see Plate] the written portion of this article is very much abridged.

Two columns at the left show the time of high water, and approximately the hour of the moon's southing on the same day. The period which should elapse between the meridian passage and high water is subject to so many collateral influences that it is not determined without long continued observations. But for the same place it must be nearly constant, and a tide arising from that cause would therefore occur with regularity. The space occupied by the corresponding strength and direction of the winds, as observed locally, exhibits only their prevailing or general condition.

On the 22d of September only four hours passed without observations, but most of the days began at 5 A. M. and closed at 7 P. M.

The position of Green Bay is more favorable for detecting a lunar tide, if it exists, than a point on the shore of the lake. In inland seas of much greater size, such as the Baltic and the Mediterranean, which connect directly with the ocean, only a small tide is observed. I am not aware that it has been noticed in the Caspian and the Black Seas. On the open sea the rise and fall is slight, ranging from two to three feet only.

The great vertical range of tides in our harbors on the coast arises from the configuration of the shore and the form of the ocean bed. The swell is augmented of necessity as it is driven into bays and inlets with converging shores and shallow water. At the mouth of the Bay of Fundy the tidal wave has thus been raised to 10 and 12 feet, and running into the bay it attains a height of 30 and 40 and at spring tides of 60 feet. The contour of Green Bay is much the same. A swell of two inches at the Port des Morts when carried on and compressed between the converging shores should produce a rise of six or eight inches.

It has been long known that on the western lakes there is a land and water breeze occurring daily, as happens on the coast of the ocean. Its regularity may be disturbed by storms, but without these a breeze begins gently to draw off shore between seven and eight in the evening, sufficient to take vessels out of harbor. About ten in the morning following, the reverse is witnessed. In the cold months, a sluggish, but damp and chilly, current of air moves from the water towards the land. It is productive of congestion of the skin, oppresses the lungs, produces torpor in the animal system, and increases the flow of blood to the head. The evening breeze has the opposite effect. Without assuming, in the present state of the observations, that the moon produces no perceptible effect on the waters of the lakes, I offer some deductions that I think follow from the reg ister of Mr. Underwood, showing a direct connection between the winds and the rise and fall at Green Bay.

This effect is complicated but may be philosophically explained. A land breeze commencing at the Port-des-Morts, would in due time press the waters into the bay, more or less according to its duration and force. A water or off-land breeze would depress the water, but owing to the form of the bay and the coast the effect should be less in amount. These breezes are regular.

The winds and gales that occupy the whole surface of the lake, are irregular in their occurrence. They overcome in many cases the minor currents that flow and reflow across the shore line otherwise daily, to and from the land. These limited currents arise from the unequal heat of the day and of the night. Suppose a powerful norther is raging on the lake, driving the navigator towards its southerly extremity, where the chances of

shipwreck are at least equal to those in favor of his escape. The gale carries the water along with it, and at Chicago and Michigan City there is a rise in the surface of three to four feet. At the Beaver Islands and at the Port-des-Morts there is a corresponding depression. The waters of Green Bay must therefore tend to flow out. But the same wind operating within the basin of the bay, resists the flow of water to the north, and diminishes the result that would otherwise follow, depressing the surface at the town of Green Bay. A gale from the east and northeast acts in favor of a rise, both directly and indirectly. Its tendency is to force more water into the bay and to retain what is already there. Accordingly we should anticipate very high water under the influence of prolonged northeasterly winds. But even here as I witnessed at the Oconto River, November 2d and 3d, 1858, a reflux may occur while the wind holds in the same quarter. On the 2d at noon the water was at its greatest known height. At noon on the 3d it had fallen 12 inches although the same gale continued.

Gales from the south and southwest should produce hydrographical effects the reverse of those from the north, and have the same double action. If they continue long, the water in the lake is raised at its northerly end, and tends to flow into the bay, raising its surface. Within the area of the bay, however, the tendency is to drive water out of it, and to depress the surface at the mouth of the Fox River. Here is again the question of the resultant of opposing forces.

The diagram and its attendant columns show a direct connection between the northeast winds and the extreme floods of the season. The 2d of July, the 20th, 21st and 27th of August, the 8th, 9th and 24th of September, and the 2d and 3d of November are cases of this sort.

But to present this part of the subject more fully I insert a table of the extremes of both the ebb and the flood during 29 days which have the fullest record. [See table, next page.]

From this table it appears that in all cases where the force of the wind during the day reached 2 and over, there was a differ ence of level of eight inches or more, with the exception of Sept. 1st, when it was only 6 inches. The wind that day was southerly. There is one case (Sept. 9th) of a range of 8 inches where the force of the wind (northeast) was only 1. In another case (Sept. 25th), where the record of the previous day was not taken, there was a fluctuation of 10 inches without any wind observ. able at the town of Green Bay. Observations on the coast are necessary to elucidate such cases. On the 25th also there was a range of 9 inches under similar circumstances.

By the registers, there were 17 days in which the flood oc curred twice, having two maxima, and 15 days with but one.