ON SUNSPOTS AND BAINFALL. 



231 



thirteen terms are reduced to eleven, and these, for convenience, are 

 called the ' mean cycle.' 



I. — Sunspots. 



8. Applied to Wolf's relative numbers of sunspots (latest edition), 

 the above method gives the following results for the years 1811-77 : — 



Table 1. — Sunspot numbers. — Maximum years in 6th line. 



■9. In the above table all the sunspot numbers for the maximum 

 years 1816, 1829, 1837, 1848, 1860, and 1870, are in the sixth, horizontal 

 line, and the places and the numbers for the minimum years are denoted 

 by asterisks. The " means " for the thirteen terms or series of years are 

 given in the eighth column, and they show that the sunspots increase 

 from ll - 6 in the second term to 100 - 4 in the sixth, and then decrease to 

 20 - 5 in the twelfth. The " mean cycle " in the next column is formed as 

 follows : — a, b, c, &c, being the first, second, third, &c, terms of the 



+ 2Z> + c 



"means" 



the numerical value of 



is made the first term of 



the " mean cycle," the numerical value of ^ its second term, 



and so on. The " variation " in the last column but one is the deviation 

 from the mean value of the " mean cycle." 



10. "With the exception of 1833 and 1867, which are respectively in 

 the third and tenth horizontal lines, the years of minimum sunspots are 

 all in the first, second, twelfth, and thirteenth lines (or terms), and all 

 the minimum sunspot numbers, except those for 1833, contribute to the 

 formation of the first and eleventh terms of the " mean cycle." It would 

 be better not to have the sunspot numbers for 1836 in the thirteenth 

 line ; but their position cannot be altered without altering the position of 

 the maximum year 1829, and the main object of this table is to obtain 

 approximate values of the sunspots for the mean maximum year, and for 

 one or two years on either side of it. 



11. Some of the years are necessarily repeated in the succeeding 

 series, but this does not materially affect the " means " or the " mean 

 cycle," the average of the latter being 48 - 8, while the average value of 

 the sunspots for the whole period (1811-67) is 46*9. 



