Both had a nucleus, and both had tails, which were parallel to each other. The comets continued to travel together until the 15th March 1846, when the new comet began to fade away, until, on the 24th March, the old comet only was visible, while in April both had disappeared entirely. A similar phenomenon was again observed at its next passage in 1852, but since then Biela's Comet has entirely disappeared. It is suggested by astronomers, that the comet has become condensed, and broken up, forming a shoal of meteors. Support is lent to this theory by the fact that in November 1872, when the earth was passing through space and had arrived at that part of its orbit which intercepted the orbit of Biela's Comet, instead of the comet being seen, the earth came into contact with a swarm of meteors, and this is accepted as evidence that Biela's Comet was condensed far away in the colder regions of interplanetary space into a more solid form of matter, known as meteors. One of the more famous of the short period class of comets is that known as Halley's Comet, which has a period of about 76 years. This comet has been seen in its return journey to the sun about 25 times. It was named after its discoverer, Edmund Halley. He was led to identify this comet with that of 1531 and 1607, and thus to conclude that it had a period of 75 or 76 years. He therefore predicted its reappearance in 1759. As the year approached, its arrival was eagerly looked for, to see if the prediction would be verified. It was thought, however, by a certain astronomer named Clairaut, that the larger planets, as Saturn and Jupiter, might interfere with its orbital motions, and after careful calculations a difference of 618 days was allowed, which brought its anticipated reappearance down to April 1759. It actually reappeared in March of that year. Its next reappearance was fixed to take place about November 1835. The comet became visible on 5th August 1835, and continued to be seen till April 1836, when it again disappeared. As the reappearance of the comet was calculated by the application of the Newtonian Law of Gravitation, such a result only gave added confirmation to the application of that law to cometary bodies. Of the Long Period Comets there are several known. That of 1858 has a period, it is thought, of 2000 years. The 1811 comet has a period of 3000 years, while that of 1844 has a period of over 10,000 years. All these comets move in orbits of such great size that their return is improbable. One of the characteristic features about Long Period Comets is their great brilliancy and size.