38o THE POPULAR SCIENCE MONTHLY. 



other important factors — barometric changes, winds, magnetic and 

 other phonomena. The conclusions of this paper are deduced only 

 from the data presented. Let us now compare the curves. 



The maximum temperature periods of 1839, '49, '60, '70, and '82 at 

 Detroit will correspond to the minimum rainfall periods of 1839, '50, 

 '60, '72, and '86 — if we credit to the latter a lag or interval behind the 

 temperature periods of to 4 years. The minimum temperature peri- 

 ods of 1834, '43, '55, '66, and '75 correspond to the maximum rainfall 

 years 1836, '44, '55, '68, and '80, with a lag varying from to 5 years ; 

 the mean of the lag being 1*8 years. 



If this showing reverses the commonly received opinion that high 

 temperature is followed by extreme rainfall, I can only say that the 

 facts, as I find them, do not warrant such conclusion. Let the reader 

 attempt to connect cither the maxima or the minima of the curve of 

 temperature with the like periods of the rainfall, and he will find it 

 necessary to admit intervals of from six to nine years, a conclusion 

 which would be inconsistent with any influence whatever. 



I now turn to another element, or phenomenon, which will be found 

 to have an intimate bearing upon our investigation. 



Recently, much speculation has been elicited by the ascertained 

 periodicity of spots on the sun's disk. It is now an admitted fact that 

 the increase and decrease of the spots affect the magnetic needle, and 

 influence the earth's magnetic and electrical condition. The extent to 

 which these affect the meteorology of our planet is a moot question 

 with the learned on these subjects. 



Some noted observers in Europe and India maintain the theory of 

 an influence exerted by the sun-spots upon the rainfall, and this di- 

 rectly as the number of the spots. In this lake region, attempts to 

 establish or define these relations have been few and unsatisfactory. 

 It will be my part to show that the sun-spots do decidedly influence 

 the temperature, and indirectly the rainfall, and that the curves of 

 temperature correspond directly with those of the sun-spots. This 

 correspondence holds not only as regards the maxima and minima 

 periods, but as to the general features of the two curves. 



Wolf's tables of the sun-spots from 1769 to 1882 show ten periods 

 of maxima and as many of minima, the spots ranging from in a 

 minimum year to 150 in a maximum year. Of these periods, one half 

 are embraced within the sixty-six years from 1769 to 1834. For this 

 cycle there are no reliable statistics of temperature and rainfall ; so that 

 my data are confined to the sun-spots and the lake periods, of which I 

 present a tabular statement, as supplementary to Diagram No. 1. 



Table No. 1 exhibits in groups : 



1. The years of maximum and minimum sun-spots from 1769 to 

 1834, according to Wolf's numbers — the maxima and minima in sepa- 

 rate columns. 



