CLIMATE OF THE LAKE REGION. 385 



3. That the times of maximum and minimum rainfall occur 

 inversely as the temperature, and follow after, with mean intervals of 

 one to four years. 



4. That the times of maximum and minimum temperature occur 

 dlrectlif as the sun-spots, with small or no intervals. 



5. That the times of high and low water of the lakes and river 

 follow behind the sun-spots, inversely, by a double lag — of lake be- 

 hind rainfall and of rainfall behind sun-spots — the mean of both 

 being four years. 



6. That the periods of maximum and minimum sun-spots, tempera- 

 ture, and rainfall have an intimate relation to each other, and that this 

 relation appears in the respective periodicities, which differ but little, 

 while the means are nearly identical. 



The question naturally arises. How far do the conclusions here 

 recorded afford a foundation for forecasting the meteorology of the 

 future ? 



If all the wave periods were of equal lengths and time?, with suffi- 

 cient allowance made for other factors not within our present discus- 

 sion, we ought to do so with exactitude. But though our sovereign 

 governor — the sun — exhibits a considerable degree of regularity in the 

 increase and decrease of his spots, he has not as yet admitted us into 

 the secret either of the cause or of the extent and frequency of his 

 variations. 



We have also seen that while the curves of temperature and rain- 

 fall are controlled by the sun-spot periods, their times of maxima and 

 minima are not therefore synchronous. This is true to some extent 

 as between the sun and the temperature, while those of the rainfall 

 are not only inverse to, but lag behind, the temperature extremes, 

 with varying times. There follows, therefore, a difference, both in 

 the lengths and the times of the periodicities of each.* Owing to 

 this lag, and its variation in time of one to four years, it follows that 

 when the temperature curve is at its maximum or its minimum, that 

 of the rainfall is not necessarily at its lowest or its highest. In fact, 

 such a conjunction may be brought about in the progress of time, that 

 a wet period may correspond in time to a warm one, or nearly so, and 

 vice versa, and yet the law of opposites continue absolutely persistent. 



This observation applies with even greater force to the lake curves, 

 the lag in which is uniformly greater than in those of precipitation. 

 Thus it has happened three times within the last half-century that 

 high water in Lake Erie has corresponded in time with a high sun- 

 spot period. 



We observe, also, in noting the curves of temperature, as each ap- 

 proaches its low extreme, a sudden dropping of the temperature from 



* While the periodic times in the curve of temperature range from nine to twelve 

 ears, those of rainfall range from eight to fifteen. 

 VOL. XXXII. — 25 



