The Perseids usually appear, with no remarkable variation in numbers,
every August, maximising about the 12th. They have a parent, Comet Swi
ft-Tuttle (1862 III), and, with the exception of planet Earth, the cau
sative meteoroids keep away from perturbing planets. Of all the known
streams the origin and evolution of the Perseids should be the easiest
to understand. The meteoroids are fast and are prone to fragmentation
.