376 THE POPULAR SCIENCE MONTHLY. 



As to low extremes, it seems well ascertained that the one of 1819- 

 '20 was the lowest known prior to 1841 — the low depression which 

 succeeded the extreme elevation of 1838. Presumably it was the 

 lowest known during the century. Old Frenchmen of Detroit had no 

 tradition of a level below that of 1819. Statements regarding the 

 stage of the water always make reference to the acknowledged high- 

 est and lowest years. Thus we are enabled to fix upon and determine 

 with considerable exactness the relative values of other low periods. 

 The water in 179G was reported by lake captains to be universally 

 low, and indicating a level five feet below the high extreme of 1838. 

 From that year, they say, it rose rapidly, and continued to rise until 

 1800. Colonel Whittlesey says :" It was ascertained generally that 

 the water was low in 1790, 1796, 1802, and 1810. Between February, 

 1819, and June, 1838, there was a continual rise, amounting to G feet 

 8 inches." Old settlers compare the low stage of 1802 with that of 

 1797. In 1806 it was reported at Cleveland lower than in 1801-02, 

 and declining regularly to 1809-'10. At this date it was reported 

 nearly as low at Buffalo as in 1819. From 1828 it was reported as 

 falling, and in 1833 was 3 feet 10 inches below June, 1838. From this 

 year on we are able to trace the "secular" periods of lake and river 

 with considerable accuracy ; and data also exist in regard to other 

 elements which it is proposed to include in our discussion. I give two 

 diagrams, intended to exhibit graphically what is shown more in detail 

 in the tables. 



Diagram No. 1 shows the curve of high and low water of Lake 

 Erie fronn 1788 to 1838, constructed in accordance with the above 

 data. In coimection with it is given the sun-spot curve, from 1769 

 to 1838, according to Wolf's tables, reference to w^hich will be made 

 hereafter. The lengths of the periods are also shown, and the lag of 

 the lake periods behind the sun-spot periods. 



Diagram No. 2 gives similar data for the term of years from 1834 

 to 1887, including, in addition to the curves of lake-levels, those of 

 the rainfall and of the temperature (registered at Detroit), and of the 

 sun-spots, according to Wolf's tables. 



In these diagrams my endeavor has been to exhibit by curved lines 

 the recurring maximum and minimum periods, eliminating intermedi- 

 ate and irregular fluctuations. 



Confining our attention for the present to the curve of rainfall 

 (Diagram No. 2), let us endeavor to ascertain whether among the 

 many and often ahru]it fluctuations it is possible to discover any pe- 

 riodicity. 



The vertical columns represent years. In the portion devoted to 

 the rainfall variations the horizontal lines represent the number of 

 inches of annual precipitation. 



It will be noted that the years 1836 and 1880 were times of excess- 

 ive rainfall. Between these two extremes, and about equidistant, 



