1^st α period < 2 (*), troughs:

Lasting years

2^nd α period < 2 (**), troughs:

Lasting years

3^rd α period < 2 (***), troughs:

Lasting years

1^st, 1746-1753 (not shown in the above figure)

7

1^st, 1875-9

5

1^st, 1948-51

4

2^nd, 1765-1774

9

2^nd, 1883-86

4

2^nd, 1954-5

2

3^rd, 1784-1791

7

3^rd, 1890-97

8

3^rd, 1958-69

12

4^th, 1820-1825

5

4^th, 1901-10

10

4^th, 1971-2

2

5^th, 1826-1836

10

5^th, 1921-5

4

5^th, 1975-78

4

6^th, 1841-1852

11

6^th, 1928-37

9

6^th, 1982-87

6

7^th, 1858-1870

12

-

-

7^th, 1998-02

5

-

-

-

-

8^th, 2009-18

10

Average round

9 (8.71)

7 (6.67)

6 (5.62)