Solar cycle
Solar cycle 10 was the tenth solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 11.3 years, beginning in December 1855 and ending in March 1867. The maximum smoothed sunspot number (SIDC formula) observed during the solar cycle was 186.2 (February 1860), and the starting minimum was 6.0. During the transit from solar cycle 10 to 11, there were a total of 406 days with no sunspots.