Sir Edmund Halley is credited with making the first observations
of Baily’s beads during the eclipse of 22 April 1715. They were also seen
by Maclaurin from Edinburgh during the annular eclipse of 1 March 1737 and
by Williams from Revolutionary War America on 27 October 1780 from just outside
the path of totality. But it was Francis Baily’s widely–disseminated description
of the phenomenon during the annular eclipse of 15 May 1836 that led to their
bearing his name thereafter.
Up to 15 minutes before totality, tiny specks of light called "Baily's Beads" make their brief appearance. They are caused by sunlight shining through the valleys on the edge of the Moon as the edge of the Moon is not smooth but jagged with mountain peaks. These points of light are spaced irregularly around the disappearing edge of the Sun, forming the appearance of a string of beads around the dark disk of the Moon. When a single point of sunlight remains, a beautiful "diamond ring" effect is created against the outline of the Moon. This final sparkling instant signals the arrival of the moon's shadow. Baily's Beads and the Diamond ring are seen again in reverse order at the end of totality when the Moon moves away from the Sun.