CLIMATE OF THE LAKE REGION. 



381 



2. The years of maximum and minimum levels of Lake Erie, which 

 are given in feet and tenths below the plane of 1838 — the maxima and 

 minima in separate columns. 



3. The lag, or interval in time at which the periodic changes in the 

 lake follow inversely those of the sun-spots. One column gives the 

 number of years lag of the lake maxima behind the sun-spot minima ; 

 the other of the lake minima behind the sun maxima. 



4. The sun and lake '■''periods.'''' In one column are given the 

 number of years between each maximum of sun-spots and the next 

 preceding maximum, and alternately, the number of years between 

 each minimum of spots and the preceding minimum. In the other 

 column are given the like data for the lake periods. 



TABLE No. I. 

 Maximum and Minimum Periods of Sun-Spots and Lalce Erie, 1769-1834,. 



The phenomena which this table makes apparent are : First, that 

 what I have called the sun and lake periods approximate in length, 

 and the means of each are nearly identical — 12"3 and I2'6 years. 

 Second, that the sun and lake periods are not synchronous, but that 

 the changes in the lake follow at considerable distance (lag) behind 

 the sun-spot times. Also that the lake maxima lag behind the sun- 

 spot minima less than do the lake minima behind the sun-spot maxima, 

 the means being, respectively, 3*5 and 4*5 years. That is to say, the 

 waters fall less rapidly than they rise, by the mean of a year. We 



