Page:Popular Science Monthly Volume 32.djvu/389

Rh extent. In discussing this so-called "secular" variation it becomes necessary to procure data from outside sources.

Milwaukee represents well Lake Michigan, and Cleveland Lake Erie. Each is about half-way between the head and foot of the lake upon which it is situated, and where the changes may fairly be considered as means of the whole. From Milwaukee I have a table of the rainfall from 1844 to 1886, and of the "secular" variations of Lake Michigan from 1859 to 1882. From Cleveland, of the rainfall from 1856 to 1886, and of the lake variations since 1859,

At each of these places the standard or plane of reference is the high water of 1808. The standard at Detroit is an arbitrary one, namely, the water-table at the Hydraulic Works, The mean of the last fifty years is five feet below that standard, and corresponds, as nearly as I can determine, to one foot below the mean of 1838, and two feet below the extreme of June of that year.

Of the fluctuations of the water prior to the period mentioned the only data are derived from the recollections of old settlers. These, though often indefinite and sometimes faulty, are yet of great value.-Dr. Houghton, in his report of 1839, gives certain concordant statements of old inhabitants, going back as far as 1800. In a paper published in "Smithsonian Contributions," volume xii. Colonel Charles Whittlesey has collected items from all sources within his reach, going back as far as 1788. Vague as many of these details are, there is so much that is of definite value, that it seems to me possible to construct a curve of the levels of Lake Erie for the whole period, which should exhibit, with tolerable accuracy, the highest and lowest extremes at least. As I propose to use these aids in formulating certain conclusions, I ought here to give the reader opportunity to form his own judgment as to their value and authority.

To begin, it may be taken as universally admitted that the lakes were at a higher level in 1838 than at any known period before. In confirmation of this is the fact, among others, that forest-trees of a century's growth and more were killed by the high water of that year. Two other eras of very high water are reported by tradition, the one in 1814-'15, the other in 1788. Facts and comparisons reported render it nearly certain that at both these periods the levels attained to somewhere near the standard of 1838. At the former date much land and many buildings were submerged on the Detroit and St. Clair Rivers. Many statements also bear upon the fact of high-water periods between the several dates mentioned. Dr. Houghton relates, on the authority of Colonel Henry Whiting: "Old inhabitants agree that the water was very high in the years 1800 to 1802, roads along Detroit River being completely inundated, and even rendered impassable." And further, that in 1821 the river began to rise, "and in 1828 had again attained the elevation of 1815, submerging wharves that had been built in the interval; and it so remained until 1830."